Exploration Station Educator Guide

Transcription

Educators’ Manual
for Carnegie Science Center’s
EXPLORATION STATION
Table of Contents
TOPIC
TABLE OF CONTENTS
USING THIS GUIDE
EXHIBIT MAP
AIR CANNON
ANIMAL ADAPTATIONS AREA
ANIMATION STATION
BUILD-A-CRITTER
CIRCUIT TABLE
DIGITAL DRUMS
DOMINO STATION
LASER HARP
MARBLEWORKS
MOBILE STATION
NEWTON’S CRADLE
PLUMB CRAZY
POLYGONAPALOOZA
PVC PIPES
REBOUND
RIVERSCAPE
ROBOTIX TABLE
ROLLER RAMPS
SOUND DELAY TUBE
STROBE SCULPTURE / STROBE STATION
STRUCTURES STATION
STUNT FLYERS
VELCRO WALL
BIBLIOGRAPHY
WEB SITES
CONNECTIONS TO NATIONAL STANDARDS
GRADES K-4
GRADES 5-8
GRADES 9-12
sound
animal adaptations
light / optics
animal adaptations
electricity
sound
mechanics
light / optics
mechanics
mechanics
momentum
engineering and design
sound
momentum
water
mechanics
sound
light / optics
mechanics
air / flight
animal adaptations
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Elaine Catz
Education Division
Thanks to Ann Ensminger, Education Coordinator for Exploration Station and SeaScape,
for her input and editing.
© 2000, 2003 Carnegie Science Center. Educators and educational institutions may reproduce portions of this document
for nonprofit purposes, with proper attribution to Carnegie Science Center. No portion of the document may be used for
any commercial applications without express permission from Carnegie Science Center. Please direct inquiries to
Education Division, Carnegie Science Center, One Allegheny Avenue, Pittsburgh, PA 15212.
The Education Division at Carnegie Science Center welcomes
YOU to Exploration Station!!!
USING THIS GUIDE
We believe that all educators can use our exhibits to further enhance their
students’ understanding of concepts studied in the classroom. We hope that the
information and activities included in
EXHIBIT MODULE NAME SCIENCE TOPIC
this exhibit guide will help you to do just
Description of exhibit component.
that.
In this guide, you will find the following
information:
•
A map of Exploration Station
depicting the location of each exhibit
module on the exhibit floor.
•
A Table of Contents located next to
the map.
•
A detailed description of each
component, formatted as shown.Æ
•
A bibliography of sources.
•
A list of Internet resources.
Please note: While the Carnegie Science Center
staff make every effort to keep all of the exhibits
in working order, exhibits are occasionally
removed from the building for maintenance. If
you are especially interested in studying a
specific exhibit, please call ahead to verify that it
will be fully functional.
EXHIBIT OVERVIEW
Text Panel:
Text accompanying exhibit modules appears
in boxes bordered by double lines.
The BIG Idea:
(the main concept underlying the exhibit)
Background Information:
(what you need to know to understand this exhibit)
Try this at school:
Related hands-on science activities to try at
school appear in boxes bordered by thick lines.
Visit suggestions:
Things to think about and try during your visit
appear in the boxes bordered by thin lines.
Sources:
(a list of the sources used to compile the information
above including books, magazine articles, and web
sites)
Exploration Station is a fun-filled,
action-packed permanent exhibit, located on the fourth floor of Carnegie Science
Center. Since its opening on February 19, 2000, Exploration Station has given
children in grades 2-8* and their accompanying adults, a myriad of opportunities
to discover science concepts while engaging in open-ended activities.
As its name suggests, this exhibit encourages visitors to explore a wide variety of
science topics in an informal learning environment. Because few instructions are
provided, students may experiment freely with materials and concepts, learning
by doing, without having to reach predetermined conclusions. This open setting
also enables educators to create and implement their own goals and objectives for
their students’ visits.
* A portion of Exploration Station, Exploration Station Jr., is sectioned off and designed
exclusively for younger visitors, ages 3-6.
Page 2
Heinz Exhibit
EXHIBIT MAP
WORKS THEATER ENTRANCE
Animal Adaptations Area
Entrance to
Exploration
Station Jr.
Mobile
Station
RiverScape
Polygonapalooza
Velcro Wall
Roller Ramps
Strobe Sculpture
Plumb Crazy
Weather
Vision
Structures
Station
(Large)
Newton’s
Cradle
Structures
Station
(Small)
Sound
Delay
Tube
Circuit
Table
Build-ACritter
Stunt
Flyers
Robotix
Table
Animation
Station
Rest
Rooms
Rebound
Digital
Drums
Domino
Station
PVC
Pipes
Air Cannon
Strobe Station
Laser Harp
ELEVATOR
RAMP (ENTER HERE)
Page 3
ALCOSAN
Exhibit
Ecostation
AIR CANNON
SOUND
Visitors aim a large metal drum at a wall,
pointing a hole cut in the bottom of the drum
toward a moveable wall hanging. They then
hit the drumhead with their hands, observing
the effects on the wall hanging.
Text Panel:
“3...2...1...Fire!”
“What are you doing?”
“By thumping the back of this drum HARD, I squeeze a lot of air out the small
hole.”
“The compressed air creates a pressure wave which moves the sequins. ”
“A sound wave is also a pressure wave, and acts like the air from the cannon.”
“What happens when you vary your hits?”
The BIG Idea: Sound carries energy through a medium in the form of pressure
waves.
Sound is generated by vibrating objects. The vibrations produce waves that have
areas of high and low pressure. The low-pressure areas are called rarefactions,
while high-pressure areas are called condensations. Each condensation and
rarefaction make up a sound wave.
oil drum
drumhead
Condensations (pulses of higher air pressure)
hole in
drum
wall
Rarefactions (pulses of lower air pressure)
When the drumhead is struck, the vibrations of the drum-material transfer energy
to the air molecules inside of the drum. Pulses of varying air pressure travel
through the drum and out the hole toward the wall. Note that the pulse travels
through the air, not the air molecules themselves. The energy in this sound wave
eventually acts on the wall hanging to produce movement that can be seen.
Page 4
AIR CANNON
SOUND
Try these at school:
Make your own Air Cannon
(Source: Adapted from: Nye, Bill, et al. Family Fun Science!
1998.)
Materials
• Empty ½ liter water or soda bottle
• Rubber band
• Matches
Procedure
• Cut the end off of the bottle:
•
•
Demo Tape, KCTS Television,
Plastic wrap
Candle
Take a piece of plastic wrap
(approximately 1 square foot) and
fold it in quarters.
•
Cover the cut end of the bottle with the folded piece of
plastic wrap and secure it with a rubber band.
•
•
Place a candle (in a holder that won’t tip over) at one end of a table.
•
Light the candle.
Aiming the open end of bottle toward the candle,
tap on the plastic sheet. With a little practice, you
should be able to snuff out the candle.
•
Whelmer #1: Air Cannon
http://www.mcrel.org/whelmers/whelm01.asp
(Source: Jacob, Steven. “Air Cannon.” Whelmers. McREL Accessible Science Series, 1997. )
Description: This device shoots a "cannon ball" of air up to 100 feet.
Materials
• 5 gallon plastic bucket or small trash can
• Rubber sheet (shower curtain, tarp, etc.)
• Large hose clamp or string and duct tape
• Saw or cutting blade
• Dowel or drum-beater
Instructions
• Cut a 2.5 to 3-inch circular hole in the center of the bottom of the bucket. Stretch a
sheet of thick rubber or shower curtain over the open end of the bucket. Secure and
seal it with a long hose clamp or use string and duct tape. Strike the "drum" head with
a dowel or drum-beater. A puff of air will shoot out of the hole in the bottom of the
bucket, traveling the length of a classroom.
Presentation
• Ask a student to look in the bucket and describe the contents. (Most will make a quick
response and say "There's nothing in the bucket.") Repeat the inquiry, asking them to
think before responding. Elicit the response that the bucket is full of air. Remind
students that scientists pause and think before responding to questions.
• Ask students to share where they have seen or experienced any device or
phenomena similar to the air cannon (nozzles on garden hoses, bellows, water gun,
spitting a watermelon seed, etc.; any situation where pressure is applied to a liquid or
gas being forced through a constriction).
Page 5
AIR CANNON
SOUND
Content
• This activity demonstrates the fact that air occupies space. As the rubber sheet is
pushed into the interior of the bucket, the volume decreases and the pressure
increases. The increase in pressure forces some of the air out of the hole. The velocity
at which the air leaves the bucket is inversely proportional to the diameter of the hole;
the smaller the hole the greater the velocity of the air. Students may have experienced
a similar phenomenon as they constrict a garden hose to increase the velocity of the
flowing water.
• The proper name for the air cannon device is vortex generator. The "ball" of air that
shoots out of the cannon is actually a flat vortex of air, similar to rings of smoke blown
by a talented cigar smoker. A vortex is generated because the air exiting the bucket at
the center of the hole is traveling faster than the air exiting around the edge of the hole.
That swirling or vortex motion can be observed if a little smoke is blown into the bucket
just before giving the rubber membrane a gentle push.
Extensions
• Allow the students to examine a garden hose and nozzle, a bellows, a cake
decorating tube and points, or other devices that constrict the flow of air, water, or
other substances. Ask them to describe how they work.
• Give students the same equipment used to construct the air cannon and challenge
them to make a cannon that can blow out the flame of a candle that is placed a set
distance from the position of the air cannon. They can construct as many cannons as
they wish to devise the most effective one. They should describe the variables that
make this cannon successful.
© Copyright 1997 – 2000, McREL
Visit suggestions:
Have your students experiment with the Air Cannon, paying attention to the following:
•
•
•
•
Standing next to the Air Cannon, face the wall hanging and swing your arm toward
the wall as if you were hitting the drumhead. Now repeat the action, actually hitting the
drumhead. Compare the responses of the wall hanging. Why are they so different?
What happens if the drumhead is tapped lightly? Compare the wall hanging’s
reaction with the one that occurs if the drumhead is hit hard.
When the cannon is aimed straight ahead and hit, which part of the wall hanging
reacts the most? How much of the reaction is a direct result of the moving air? Why
do other parts of the wall hanging move?
Trace the path of energy transfer starting with your breakfast and ending with the wall
hanging.
sound
Example:
FoodÆ chemical energyÆ kinetic energy of musclesÆ vibration of drumheadÆ vibration of air moleculesÆ
vibration of wall hangingÆ sound
Sources:
“hearing and listening.” Idea sheets. school in the exploratorium. The Exploratorium, 3601
Lyon Street, San Francisco, CA 94123, 1976.
Hewitt, Paul G. Conceptual Physics. 3rd ed. Boston: Little, Brown and Co., Inc., 1977.
Walpole, Brenda. 175 Science Experiments to Amuse and Amaze Your Friends. New York:
Random House, 1988.
Page 6
ANIMAL ADAPTATIONS AREA ANIMAL ADAPTATIONS
Visitors are given the opportunity to view a diverse variety of live animals, each
in its unique habitat. By considering the animals and their natural environments,
visitors discover how various adaptations enable animals to survive in different
types of climates.
Text Panel:
All animals have special body parts and special behaviors that can help them to
survive.
These adaptations help animals live in their habitats. An animal living in the
desert has different body parts and behaviors than an animal living in the ocean.
The animals have different ways to find food and eat it, drink, reproduce, and
escape from danger.
To find food an animal might have claws for digging, antennae for smelling, or
snouts for drinking.
Animals’ bodies also help them to protect themselves. Shells, horns, hooves,
exoskeletons, and tails allow animals to defend themselves.
Because fighting uses up a lot of energy, it is usually the second choice.
Camouflage, hiding, wings, strong legs, or fins help animals to get away from
danger first – before needing to fight.
Have a look at the animals here. What adaptations do you see? How would they
help these animals survive?
The BIG Idea:
Adaptations enable animals to survive.
In order to survive, animals need to be able to find food, water, and shelter. They
also need to be able to protect and defend themselves. Animal species that are
well adapted to their environments have developed special body parts and / or
behaviors over many generations that help them to thrive in their specific
surroundings.
The animals in the Animal Adaptation area live in environments similar to those
in which they would be found in nature. These animals represent a wide range of
biodiversity from different parts of the world.
During a visit to Exploration Station, the following animals are usually available
for viewing. Staff and time permitting, Science Center Presenters are able to
remove some of the animals from their tanks to give visitors a closer look.
Page 7
Madagascar Hissing Cockroach
(Gromphadorhina portentosa)
This large insect comes from the island of Madagascar, where it
lives in the Rain Forest.
Madagascar Hissing Cockroaches eat detritus (decaying matter)
that they find on the forest floor.
These insects are eaten by lizards, birds and lemurs and have
developed a unique ability to emit a hissing noise to communicate.
(Photo Source: CentralPets.com
http://centralpets.com/pages/photo
pages/insects/roaches/PHOTO_R
CH2559.shtm1 (12/13/02))
Eastern Box Turtle (Terrapene carolina carolina)
Note: Our reptiles are captive-bred, not wild-caught.
This reptile can be found in Pennsylvania forests. Its biggest
threat comes from humans – our vehicles, pesticides, land
development and illegal pet trade.
Box turtles have developed several adaptations that enable them to
survive in the forest. In addition to their hard shells, which
provide shelter and protection from predators, turtles have claws
adapted for digging and “beaks” adapted for eating fruit,
vegetation, and insects.
Uromastyx (Uromastyx ocellata ornata)
This reptile lives in desert environments and has adapted to
survive in a hot, dry place with very little water. Look in the
Uromastyx’s habitat at the science center. Can you find a water
dish? It doesn’t need one! The Uromastyx gets all of the water it
needs through its food. The lizard’s sandy brown colors provide
protective camouflage, allowing the Uromastyx to blend in with
the desert background.
Photo Source: Mike’s Turtle and
Tortoise Page
http://myweb.ecomplanet.com/PI
CC6224/PageAlbumReptile+pics
PageNumber1.htm (12/13/02)
Photo Source: Sorin, Eric.
Uromastyx Pictures and
Enclosure Images
http://www.kingsnake.com/uroma
styx/images/picomfeml.jpg
(12/13/02)
While the Uromastyx has a spiked tail for defense, it will first try
to hide from predators. The lizard can actually hide in crevices,
puff up its loose skin on its body to make a “custom fit,” and will stick its tail out of the crevice
opening to swat at any predators.
African Giant Black Millipede (Lophostreptus rutilans)
African Giant Black Millipedes come from tropical and subtropical western Africa. They are Arthropods, meaning they have
jointed legs, a body divided into segments, and an exoskeleton.
When threatened, their first line of defense is to curl up into a tight
spiral or ball. They also have the ability to secrete a liquid acid
that is irritating to predators.
Photo Source: Silver City
Serpentarium, Inc.
http://www.scserp.com/SCS_Phot
o_Gallery_Invertebrates.htm
(12/13/02)
These millipedes have developed the ability to force their bodies into rotted logs or soft dirt using
their many strong legs.
Look for tiny mites running around on the millipedes’ bodies. These mites eat tiny particles off
of the millipede. The mites get a meal and the millipede is protected from infection. This
relationship is called symbiosis.
Page 8
Teaching with Bugs
(Source: Teaching with Bugs. Teacher Guide. The Yuckiest Site on the Internet © 2000 Discovery
Communications Inc. http://yucky.kids.discovery.com/teachercenter/pg000065.htm)
Animal Behavior
* From a Bug's Point of View: It's a bug's life! Students can take on the persona of a
specific type of bug and write a "day-in-the life" profile, telling about its behavior from
sunup to sundown as if it could speak.
Animal Systems
* 3-D Bugs: Challenge students to create realistic insect models using the most
imaginative combination of materials they can find. Start them off with raisins, soaked
dried beans, Play-Doh, toothpicks and craft glue, and see what else they come up with.
Encourage them to model a specific insect variety and include its particular features.
Make a "sculpture gallery" to display the creations!
Life Cycles
* Bug Convention: Profile an unusual bug and present him to the other bug
representatives at a mock convention! Older students can create a documentary of their
convention using a video camera or still photos inserted into presentation software, or
make an annotated scrapbook.
Visit suggestions:
The contrasting habitats allow visitors to make comparisons between the animals
and their environment, what they eat, how they find shelter, and their adaptations
to their surroundings.
Sources:
African Giant Black Millipede. Santa Barbara Zoological Gardens. 2002.
http://www.santabarbarazoo.org/animals/invertebrates/millipede.html
Madagascar Hissing Cockroach. Santa Barbara Zoological Gardens. 2002.
http://www.santabarbarazoo.org/animals/invertebrates/cockroach_madagascar.html
Yucky Roach World. Discovery Channel. Discovery Communications Inc. 2000.
http://yucky.kids.discovery.com/noflash/roaches/index.html
Page 9
ANIMATION STATION
LIGHT / OPTICS
Visitors create an animated video using an overhead video camera and small
manipulatives. As they move the objects across a table, visitors repeatedly push a
button, capturing the action frame by frame. The frames are then played back on
a screen, allowing visitors to watch their own show. A large on-screen menu of
sound effects can be used to further enhance the video.
•
Note: Directions for using the Exhibit Control Panel to create an animated
video can be found on the following page.
Text Panel:
“Hey! You made a movie!”
“Yep. I moved each piece a little bit at a time, then took a picture. When I play
them back, I see an animation – a moving image!”
“The images are flashed too fast for your brain to keep up with, so you think you
see them moving. It’s called persistence of vision.”
“Movies use 24 pictures every second; television uses 30.”
“You can even add sound effects!”
The BIG Idea: Movies are made up of a series of still pictures that are shown in
rapid succession. If the pictures are flashed on and off quickly enough, the
phenomenon known as “persistence of vision” allows us to perceive motion.
Depending on its brightness, an image may be retained by the eye and brain as a
visual impression for about 1/30th of a second. This ability is known as
persistence of vision. Moving pictures (as we see on TV or in the movies) are
actually an optical illusion based on this principle. When a sequential series of
still pictures are flashed on and off quickly, the eye and brain retain images that
fill in the between-the-picture gaps.
A movie projector shows 24 frames/second with each frame projected twice.
When watching a film, the eye sees 48 separate pictures per second (2 of each
individual frame) and the eye and brain retain the images in between the frames
long enough to result in the illusion of motion.
Page 10
ANIMATION STATION
LIGHT / OPTICS
Try this at school:
Make a Flickerbook
http://www.tpt.org/newtons/10/omnimax.html
(Source: “Omnimax: How is a giant-screen movie made and projected?” Newton’s Apple.
(6/16/2003).)
Description: Create your own version of an animated movie.
Background information
Animation is made possible because our eyes perceive two slightly different pictures, one
after the other, as a moving image. It is a physiological fact that an image is registered
onto our retina, remaining there for a bit even though the source of the image is out of
view. The eye can register 12 pictures per second as separate images, so if the pictures
appear more quickly than this, the eye perceives them as moving pictures. Motion
pictures appear at the rate of 24 photographs (frames) every second.
Films today consist of a strip of transparent acetate with a series of small, sequenced
frames, each representing a visual record of a moment in time. When the series of
pictures is projected rapidly onto a screen, the illusion of continuous action is created.
Before motion pictures were invented, people created the illusion of moving pictures by
drawing a slightly different image on each page of a book, and then flipping through the
book with a thumb. The pictures appeared so quickly that the eyes “saw” a steady
movement. The first “flickerbook” appeared around 1890. Invite your students to create a
small flickerbook.
Materials
• Pencil, pen, or markers
• Paper, needle and thread, and staples OR a small bound notebook OR a pad of
removable sticky notes
•
•
•
•
Procedure
If you are making your small books from scratch, use the paper, needle and thread, or
staples to create some books of your design. If you are using a notebook or a pad of
sticky notes, these can be your “books.”
Have each student think of a simple story he or she would like to illustrate.
On the back side only of each page, draw a picture (close to the cut edge of the
paper) in which the action is slightly different than the action in the previous picture.
When the picture story is finished, hold the book in the one hand and flip the pages
from front to back with the thumb of the other hand.
Questions
• Are there certain actions or pictures that are particularly well suited to this technology?
Are there certain actions not well suited to this device?
•
What happens if you flip through the pictures too quickly? Too slowly?
Newton's Apple is a production of KTCA Twin Cities Public Television. Made possible by a grant from 3M.
Educational materials developed with the National Science Teachers Association.
Page 11
ANIMATION STATION
?
Add
Sound
Recor
LIGHT / OPTICS
Play
Erase
One
Frame
One
Frame
Animation Station Control Panel
Visit suggestions:
Have your students create their own animated videos.
Example: Making the film, “Bird Eats Boat”:
Frame 1
•
•
•
•
•
•
•
•
•
•
Frame 2
Frame 3
Press the “?” button for help and directions, if necessary.
Press “Erase” button to erase the previous visitors’ movie – or press “Play” to view it
before starting. Each movie is erased automatically after several minutes if no buttons
are pressed.
Small foam shapes are used to create the picture in Frame 1.
Press “Record” button on Exhibit Control Panel to take a picture of Frame 1.
Each of the boat pieces is moved toward the right and the bird’s beak is opened
slightly.
Each of the boat pieces is moved toward the right and the bird engulfs the boat.
Press “Play” to view Frames 1, 2, and 3 in succession.
To add sound, advance the movie forward, one frame at a time, using the “One
Frame” buttons, until the desired frame is reached. Press “Add Sound”, and use the
One Frame arrow buttons to move through the selections on the screen. To try the
sound before inserting it into the film, press “Play”. When the appropriate sound effect
is chosen, press “Add Sound”.
Sources:
Macaulay, David. The Way Things Work. Boston: Houghton Mifflin Co., 1988.
“Persistence of Vision.” Exploratorium Snacks. 3601 Lyon Street, San Francisco, CA 94123,
1997.
http://www.exploratorium.edu/snacks/persistence_of_vision.html
Page 12
BUILD-A-CRITTER
ANIMAL ADAPTATIONS
Visitors create their own animals by attaching Velcro®-backed
legs, wings, fins, etc. to a mounted “body”.
Text Panel:
“I’m using these pieces to make my own animal!”
“Try it!”
“Most animals’ parts have a specific use. Beak or trunk? Wing or arm? Long
neck or short?”
“Think about where your animal would live, or how it would eat or move.”
“I made an ... eleroo!”
The BIG Idea: In order to survive, animals must be able to adapt to changes in
their environments. Observing the morphological (structural) adaptations of an
animal may reveal information regarding the habitat to which it has adapted.
Organisms respond to changes in their environments in a variety of ways. An
adaptation is a characteristic of an organism that enables it to better survive in its
environment. Sometimes an individual organism is able to respond to
environmental changes immediately. Sometimes physiological changes occur
within a species very slowly over many generations.
•
A behavioral response occurs when an organism changes its physical location
(by moving a few feet or by migrating thousands of miles) or engages in
cooperative social behavior with others to alter the environment.
•
A physiological response occurs when an organism regulates its own body
functions to better adapt to an environment (e.g. temperature regulation).
•
A morphological response occurs when organisms alter their physical
structure through developmental or growth responses over the course of many
generations such that they become better suited to an environment. Those
organisms best suited to the environment survive to pass on their unique traits
to their offspring.
Page 13
BUILD-A-CRITTER
ANIMAL ADAPTATIONS
Try this at school:
Make it a Habitat
http://school.discovery.com/lessonplans/activities/makeitahabitat/
(Source: Mealiea, Sue, and Lisa Wu. “Make it a Habitat.” Lesson Plan Library >6-12 Life Science.)
Description: Students will consider the adaptation of life forms through natural selection
to fill various niches and accommodate changing environmental conditions.
Grade Level: 6-8,9-12
Duration: 2-3 hours
Part I: As a class, discuss the concept of a dynamic ecosystem—a community of plants,
animals and microbes interacting with each other and their environment. The term
ecosystem describes both the living and non-living components of an area that interact
with one another. An ecosystem may be aquatic or terrestrial. Learn about several
different biomes on the Biomes Page. (See following pages.)
Form small groups of four students each. Each group should select one of the
ecosystems on the biomes page and conduct research to provide as much detailed
information as possible about the chemical, geological and physical features of the
environment. Consider the sunlight/energy, temperature, waves and other physical
features of the system. This research will enable you to design an organism suited for
living in the biome you select.
• Now, investigate several types of adaptation on the Adaptations Page. (See following
pages.) In order to design an organism for your biome, it’s important to know what
characteristics enable it to survive. Make a list of the traits you feel are most important
for an organism in this biome.
• You are now ready to design an organism uniquely adapted to the environment you
selected. Designing both internal and external body parts, your small group should
consider: body design/symmetry, diet/ acquiring food, shelter/ protection/ skeleton,
mobility, sensory ability, communication, reproduction/ life-cycle, digestion,
temperature regulation/ respiration/ metabolism, waste removal/ water regulation, other
unique adaptations/ behaviors.
• Prepare a group oral presentation complete with a sketch or model of your organism
in its environment. The presentation should answer the following questions:
1. How does each adaptation function with respect to the environment?
2. Which adaptations are the most significant (i.e., have the most adaptive value)?
• After each group has made a presentation, the following discussion questions might
be used:
1. What are some similarities between the organisms designed by each group?
2. Could the organisms co-exist in the ecosystem by occupying different habitats and
niches?
3. What happens when two species try to occupy the same niche?
4. How do animals reduce competition when food resources become limited?
•
Part II: Enter an environmental stressor into the ecosystem such as a volcanic eruption,
drought, soil erosion, toxic waste, storm, etc. Each group should reevaluate its “designer
organism” as to how well its features would allow it to adapt to the new environment.
Discuss as a class which organisms would survive and why. Explain how the process of
natural selection impacts your organism and the chosen biome.
© Copyright 2000, Discovery.com
Page 14
BUILD-A-CRITTER
ANIMAL ADAPTATIONS
Make it a Habitat -- Adaptations Page
An adaptation is a variation of structure, physiology or behavior that aids the organism’s
survival in its particular environment. Below are examples of some of the many
adaptations.
Teeth:
• Snakes: teeth slope backward to aid the retention of the prey during swallowing
• Sharks: two rows of teeth that point backward to hold prey; teeth are replaced
frequently throughout an animal’s life span
• Toothed whales (e.g. dolphins, porpoises, sperm whales): usually only have lower
teeth to catch prey, which they swallow whole
• Baleen whales (e.g. right whales, blue whales): hundreds of thin plates called baleen
used to filter plankton from the water
• Carnivores (e.g. dogs, lions): pointed “canine” teeth specialize in ripping and tearing
food; large molars crush bones
• Herbivores (e.g. deer, horses): incisors clip off grass; large, flat molars grind food
• Rodents (e.g. beavers and mice): incisors are specialized to chisel, usually do not
have canine teeth
• Elephants: the tusks are incisor teeth that have grown to be used for attack and
defense, for rooting food from the ground and for breaking branches
• Humans: omnivores have several kinds of teeth to perform many functions; tearing,
chiseling and grinding
Digestion:
A group of animals called ruminants are the only vertebrates able to extract the nutrients
from cellulose. Cellulose is a component of plant walls and can only be digested with the
enzyme cellulase, which vertebrates do not produce. Ruminants (e.g. cows, bison,
horses, deer, sheep) have a four-chambered stomach. The first chamber (the rumen)
contains a rich broth of bacteria and protozoa that can digest cellulose. After spending
time there, plant matter (now called cud) is sent back up to the mouth, where the animal
chews it again. The cud is then swallowed into the stomach proper where it is digested
fully.
Vision:
• Eyes at the top of the head: found in animals that live in the water (e.g. alligators,
frogs), fish that live on the bottom of the ocean floor
• Very large eyes: provide better night vision and better powers of all vision
• Eyes set on both sides of the head: provides panoramic view for predator detection
• Stereoscopic vision: found in predators and tree-dwelling animals; provides improved
accuracy when determining distances
Water Regulation:
Organisms that live in dry climates must have adaptations that allow them to obtain
water. Most animals can get all the water they need by drinking it; however, animals in
dry climates can get water from eating fatty seeds, which produce water as a by product
of digestion. Other animals obtain fluids from the sap of plants or from the bodies of the
animals they eat.
Because of the limited water available, animals in dry climates also have means of
conserving water. They are nearly all nocturnal, only searching for food at night when the
heat is low. They usually do not have sweat glands. Their urine is highly concentrated
and their feces are dry. To prevent water loss through respiration, they have a long nose
that cools the air and condenses the water inside the nostril before expelling it to the
atmosphere.
Page 15
BUILD-A-CRITTER
ANIMAL ADAPTATIONS
Temperature Regulation – Cold Climates:
Animals that obtain heat from external sources are called ectotherms. Mammals and
birds are called endotherms, because they maintain a constant body temperature through
metabolism and regulation.
• Animals that live in water usually take on the (usually stable) temperature of the water.
Some large fish and mammals also warm their bodies with muscle activity, fat deposits
(blubber) and thick, waterproof fur.
• Terrestrial reptiles keep their body temperature stable by absorbing solar radiation
during the day. At night they seek shelter to keep warm and to protect themselves
during the inactivity that results when they are cooled.
• Birds use their feathers to protect their bodies. They also migrate to warmer climates.
Mammals reduce heat loss in many ways. Below are a few examples.
• Body size: since heat is lost through the surface, the smaller the surface area
compared to the volume of the body, the less heat is lost
• Body shape: the sphere is the best shape for a small ratio of surface to body volume,
and it is therefore the most heat-retentive shape
• Extremities lose heat first; animals in cold climates have small ears and tails and short
legs
• Body coverings: covered with dense, fine fur that holds insulated air close to the body,
sometimes this fur even covers the soles of their feet
• Reduction of activity: another way to reduce heat loss is to limit body functions; some
mammals hibernate or go into a state of dormancy during the winter months
Temperature Regulation – Warm Climates:
Many of the ways animals keep themselves warm are used in reverse to help them keep
themselves cool.
• Shelter: warm-climate animals spend the daylight hours hiding in burrows or behind
boulders, coming out at night to hunt and forage for food
• Extremities: warm-climate animals have long legs and tails and very large ears that
contain blood vessels near the skin surface. Air blowing across the ears cools the
blood and this cools the body
• Evaporative cooling: sweating, panting and licking; however, these methods are
counterproductive if water is scarce because they also promote water loss
• Body coverings: most have fine, thin hair
Adaptations to Capture Prey: claws, tool use, mouth parts adapted to grab, hold, bite,
pierce, suck; toxins to kill or paralyze; heat sensors, vibration detectors, size and
strength, concealing coloration, acute senses, behavioral strategies: stealth, cunning,
confusion, surprise
Adaptations for Avoiding Capture: speed, hiding, freezing in position, withdrawal into shell
or burrow, dismemberment, counterattack: hooves, horns, wriggling, biting, stinging,
concealing color, acute senses, behavioral strategies: large herds, warning signals
Page 16
BUILD-A-CRITTER
ANIMAL ADAPTATIONS
Make it a Habitat – Biomes Page: A biome is a large geographic area that has a specific
climate (average temperature and rainfall).
Deciduous Forest: exists in North America, Europe, Australia, and eastern Asia
• Relatively warm summers and relatively cold winters; 75 to 250 cm precipitation per
year spread throughout the year
• Rich topsoil composed of decomposing organic material, decomposing organisms
• Vegetation: hardwood trees that drop their leaves to conserve water in the winter
• Animals: small mammals feed on nuts, fruits, mushrooms and insects; larger
mammals feed on smaller mammals; hoofed herbivores browse on shrubs and
seedlings
Ocean:
• Three-quarters of the earth’s surface; average depth of 3 kilometers; less than 40% of
the sunlight reaches a depth of one meter, and less than 1% of the sunlight that
reaches the surface penetrates below 50 meters; mostly cold and dark
• Coral Reef: most diverse of all marine communities; formed by colonial organisms
called coelenterates; rich in carbon, oxygen and dissolved minerals; movement of
waves causes constant flow of water; provides food and shelter to other marine
organisms; well-lighted and warm, temperatures seldom fall below 21ºC
• Seashore: heavy in nutrients washed from the land; more life than in open seas;
animals living there are adapted to the type of bottom: rocky, sandy, or muddy;
generally rock dwellers have specially adapted appendages to help them hold on
during tides and waves, sand dwellers do not reside on the bottom because of the
instability of the shifting sands, and mud dwellers burrow down into the mud
• Open Ocean: upper, better-illuminated waters of the ocean; warm with light; relatively
calm waters; top 300 meters
• Deep Ocean: lower 300 meters; no light, very cold
Freshwater:
• Freshwater lakes cover 1.8% of earth’s surface and running freshwater covers 0.3%
of earth’s surface; significant runoff of organic and inorganic material from terrestrial
areas nearby; temperatures vary with location; the deeper the body of water, the colder
the temperature
• Lakes and Ponds (standing water): edge of a lake is most richly inhabited; plants root
at the lake shore and grow up out of the water, other plants float on the surface;
animals include insects, snails and other mollusks, amphibians and reptiles, fish,
waterfowl, and small and medium mammals; the middle of a lake has small, floating
algae and larger, deep swimming fish; the bottom of the lake is very cold and has little
or no light, mostly bacteria and fungi live there
• Rivers and Streams (running water): characterized by the swiftness of the current,
abundance of oxygen and nutrients; principal inhabitants: insects and fish requiring
cold temperatures and a lot of oxygen
Desert: exists in the interiors of continents, especially Africa, Eurasia, and Australia
• Less than 25 cm of rainfall per year, but highly variable each year; occur between 20º
to 30º north and south latitude; warm days, cold nights
• Vegetation: mostly annuals that can go from seed to flower in the short period of time
when water is present; perennials are adapted for water storage with no leaves or
leaves that fall off during drought, or leaves that are small and leathery; all have
extensive root systems to trap water during periods when it is available
• Animals: reptiles and insects have waterproof outer coverings and water-conserving
excretions; nocturnal mammals are able to extract water from plants
• Tropical Rain Forest: exists in South America in and around the Amazon Basin, in
West Africa and in Southeast Asia, and equatorial regions
• Richest biomes in terms of numbers of species, estimated to contain at least half of
the world’s land organisms; rainfall of 200 to 450 centimeters per year, with little
difference throughout the year; length of daylight varies by less than one hour.
Page 17
BUILD-A-CRITTER
ANIMAL ADAPTATIONS
The soil is quite infertile; nutrients from fallen organic matter are quickly extracted by
the roots of vegetation which are spread out in the top-most layer of soil.
•
Vegetation: tall trees with smooth bark and no underbranches form high canopy of
large, leathery leaves; inconspicuous flowers; trees have large, thick bases to anchor
themselves; long, woody vines appear in any open spaces; epiphytes, plants that grow
on other plants, are abundant, getting their water and minerals from the humid air;
ferns, orchids, mosses, and bromeliads adapted to grow at low light intensities
• Animals: large numbers of insects and tree-living vertebrates including birds,
primates, large and small mammals and reptiles
Savanna: exists in Central Africa and South America
• Area of reduced annual precipitation; transition between tropical rain forest and
desert; 90-150 cm of rainfall each year; wide fluctuation in temperature; seasonal
drought; fine, sandy soil
• Vegetation: grasses with dense root systems can withstand extensive dry periods
• Animals: mammals are herbivores or carnivores; herbivores must have sophisticated
digestive systems capable of extracting nutrients from the cellulose-rich grasses, must
eat all the time, and need the ability to be warned of and flee from predators;
carnivores need adaptations to catch herbivores efficiently
Grassland: exists in North America (plains and prairies), Russia (steppes), South Africa
(veldt), and Argentina (pampas)
• Rich agricultural lands; periodic droughts, hot-cold seasons, rolling flat terrain, 10 to
60 cm of rain per year, warm and wet spring followed by scorching, dry summers, cold
and snowy winters
• Vegetation: mostly sod-forming grasses mixed with legumes and various annuals
• Animals: small, seed-eating rodents, large herbivores, and carnivores
Chaparral: exists mostly in western North America and the Mediterranean
• Mild, rainy winters and long, hot, and dry summers
• Vegetation: small trees and spiny shrubs with broad, thick evergreen leaves
• Animals: large herbivores move into the chaparral in the spring and out to cooler
areas in the summer; animals that stay are usually small and dull colored
Taiga: exists mostly in northern North America and northern Eurasia
• Also called coniferous forest; long, severe winters; short and warm summers: limited
precipitation (20 to 60 cm) mostly in summer; short daytime in winter and long daytime
in summer
• Ground is covered with a thick layer of needles and dead twigs, matting of fungus
• Vegetation: evergreen trees with small, compact leaves protected by a thick covering
to prevent water loss; no annual plants
• Animals: large and small mammals must have adaptations to survive during the
winter; heavy fur coats and/or hibernation are common
Tundra: exists in a continuous belt across northern North America, Europe, and Asia and
at the top of mountains
• Covers a fifth of the earth’s land surface, little precipitation (less than 25 cm per year),
less than one meter down the ground is permanently frozen (permafrost)
• Boggy during short summer when ground thaws; bitterly cold most of the year; long
winter
• Period of the year when there is no sunlight; corresponding period when there is no
night; drying winter winds
• Vegetation: virtually treeless, dominated by herbaceous plants, mosses and lichens,
all of which grow close to the ground to help them survive icy winds
• Animals: large hoofed mammals, small rodents, and some predators, migratory birds
during 2 months of summer
•
Page 18
BUILD-A-CRITTER
ANIMAL ADAPTATIONS
Visit suggestions:
Bring these materials with you: paper, colored pencils.
Have the students:
•
use the Build-A-Critter Exhibit to create a creature.
•
draw a picture of their creature.
•
write a description / draw the environment in which their creature might live.
•
justify their choice of environment: What adaptations does the creature have that
allow it to survive in this environment?
•
write a description of their creature: What does it eat? Where does it live? What
senses does it rely on? Is it nocturnal or diurnal? How does it move? Can it be
classified as a mammal, reptile, amphibian or bird? (Or does it fit into a different
category?)
Sources:
Arms, Karen, and Pamela S. Camp. Biology. 3rd ed. New York: CBS College Publishing, 1987.
Campbell, Neil A. Biology. California: The Benjamin/Cummings Publishing Co., Inc., 1987.
Hugh P. McCarthy, ed. Biological Science: A Molecular Approach. 4th ed. Lexington, MA: D.C.
Heath and Co., 1980.
“Re: What is the difference between a structural and a physiological adaptation?” The MAD
Scientist Network. ©1995-2000.
http://madsci.wustl.edu/posts/archives/mar97/852358709.Ev.r.html
Page 19
CIRCUIT TABLE
ELECTRICITY
This table contains two activities:
1) Visitors use wires to build complete circuits, connecting the table’s embedded
power supplies to electronic components such as lights, buzzers and switches.
2) Giant Light Bulb: Two copper balls flank a giant light bulb. A visitor touches
the two copper balls simultaneously, causing the light to go on.
Text Panel:
“You can use electricity to light the small lights, spin the motor or buzz the
buzzer.”
“But remember - the charge must flow in a complete loop from the batteries and
back again.”
“What combinations can you make?”
“The other activity here is to touch both copper spheres. Current flows through
you, completing the circuit.”
“This works with a chain of people, too!”
“We’ve made experimenting with electricity safe and fun here at the Science
Center, but don’t try this at home!”
1) Circuit Table
The BIG Idea: For electricity to flow, a circuit must be complete.
BUZZER
ON-OFF SWITCH
LIGHT
Page 20
CIRCUIT TABLE
ELECTRICITY
Everything in the world is made of tiny particles called atoms. Atoms are made
of protons (positively charged particles), electrons (negatively charged particles),
and neutrons (particles with no charge).
Particles of the same charge (e.g. two electrons or two protons) naturally repel
each other. Particles of opposite charge (e.g. an electron and a proton) naturally
attract each other. Enforced separation of positive and negative charges may be
maintained if work is done on the particles themselves.
•
For example, electrochemical reactions in a battery sustain a difference in the
overall charge across the battery’s terminals. This means that one terminal has
a net positive charge because the electrons have been driven away, while the
other terminal has a net negative charge because it contains an excess of
electrons.
Current electricity is the continuous movement of electrons from a negatively
charged terminal to a positively charged terminal.
+ -
A pathway that forms a complete loop, allowing electrical current to
flow is called a closed circuit.
+ -
A pathway that does not allow current to flow (an incomplete loop) is
called an open circuit.
A switch is a device that can be used to open and close a circuit. When the switch
is closed, the gap in the loop is filled in and current
+ + flows through the circuit. When the switch is open, the
loop is incomplete and electricity does not have a
complete path to follow.
closed
open
•
One component available on the Circuit Table is a tilt switch. Tilt switches
contain mercury inside a glass bulb. The two wires
to be connected are also contained in the bulb.
Closed
When the switch is tilted, the mercury makes
Open Tilt Switch
Tilt Switch
contact with the two wires and completes the
circuit. When the switch lies flat on the table, the mercury does not make
contact with both wires and leaves the circuit open.
+
Electronic components such as the light and buzzer
available at the circuit table are commonly connected in a
circuit either in series or in parallel.
•
When components are connected in series, the current
(amount of electricity flowing through the circuit)
through each component is the same. Note that if the
Page 21
battery
buzzer
light
Series circuit
CIRCUIT TABLE
ELECTRICITY
light bulb were to burn out, an open circuit would be created and any other
components connected in series with the bulb (here, the buzzer) would no
longer function.
+
•
When components are connected in parallel, the voltage
(electrical force that sends the electrons around the circuit)
measured across each component is the same. This voltage
is approximately equal to the voltage measured across the
battery. Note that if the light bulb were to burn out, the
buzzer would still be connected to the battery via a closed
circuit and would remain unaffected.
-
battery
buzzer
light
Parallel circuit
2) Giant Light Bulb
The BIG Idea: For electricity to flow, a circuit must be
complete.
The Giant Light Bulb exhibit
consists of two circuit loops (See
drawing below): Circuit A (Arms)
and Circuit B (Bulb). Both circuits
are initially “open”.
TRY THIS:
Touch BOTH copper balls
at the same time.
What happens to the
light bulb above you?
To complete Circuit A, the two
Try a chain of people, too!
copper balls must be connected
together in some way. When a
visitor touches both balls at the
same time, the circuit is complete. If one visitor touches the
copper ball located to the left of the bulb, another visitor touches
the copper ball located to the bulb’s right and the two visitors hold
hands; the circuit is also complete.
Circuit
Circuit
The actual light bulb is a component of Circuit B. Circuit B
contains a switch. This switch is controlled electrically (this is
known as an electrical relay). Once Circuit A has been
completed, the switch is activated.
In summary, when the pathway is completed between the two
copper balls, Circuit A is completed, activating the switch,
closing Circuit B, and lighting the light bulb.
Note: When both circuits are “closed”, the lamp current
flows only through Circuit B. A much smaller current
flows through Circuit A. This dual circuit system ensures that visitors are
isolated from (not in contact with) the lamp circuit.
Page 22
copper
ball
CIRCUIT TABLE
ELECTRICITY
Try this at school:
Electricity and Tennis Balls
http://www.mos.org/sln/toe/tennisballs.html
(Source: “Introduction to Current Electricity.” Teacher Resources. Theater of Static Electricity.
Boston Museum of Science, 1995.)
Objective: To demonstrate the basic concepts of DC electricity using tennis balls.
Materials
• About a dozen old tennis balls or similar balls.
Background
There are several technical terms that are useful, even vital, to understanding direct
current electricity. Using a simple, mechanical analogy with tennis balls these terms can
all be demonstrated and their relationships to one another explored. This activity is a
good problem-solving/creative thinking activity --be sure to give the students plenty of
time to come up with ideas.
Procedure
• Select a student to play the battery and another to be the light bulb. Give the tennis
balls (in a container) to the battery.
• Explain that the idea is to give energy to the bulb from the battery so that it can light.
This energy will have to be carried by something; in this case balls that represent
electrons ('balls' of charge).
• Have the battery gently toss the balls to the light bulb. The students should notice that
this can only happen for a very short while before the battery runs out of balls. Ask how
the bulb could be lit for longer.
Possible answers include having more balls (i.e. a bigger battery) or having the light
return the balls quickly. The first answer would work, but again only for a very short while.
The second answer introduces the idea of a circuit--a complete path where the balls are
returned to their starting point ready to be given more energy and used again. (By the
way, if you connect a bulb to one end of a battery only, will it light? The answer is no, but
in fact a little current will flow for a very short time just as the balls moved to the bulb and
stopped there in this demonstration, there is, however, not enough energy transferred to
cause a glow!)
•
Now ask students how we could increase the power that the bulb is receiving, and
hence make the light brighter. Obviously there are several possible answers.
One is to make the balls carry more energy by making them bigger--using basketballs or
soccer balls, for instance. This would work but in practice we are generally limited to
using electrons (tennis balls) which are small, negative charges. The bigger, positive
charges don't tend to be the ones that move.
Another answer would be to throw the balls harder. This does have a direct electric
counterpart--voltage (V). Voltage is simply a measure of how much energy the battery
gives each electron. If we send the same number of electrons, but give each one more
energy (i.e. a bigger 'push'), we obviously send more power.
A third answer is to send the balls over at a faster rate, that is, send more balls over each
second. This corresponds to current (I), or amperage. The electric current is simply how
many electrons pass by each second (though we actually count groups of electrons,
since they are so small and there are so many of them!) Clearly, if we send twice as
many identical electrons each second we are sending twice the energy.
Page 23
CIRCUIT TABLE
•
ELECTRICITY
Another thing we could do is both of the last two at once--send more balls, harder.
This brings up a very simple equation: The total power (P) is simply the product of the
number of balls and how much energy each one has. In electrical talk we would say
that power is the product of the current and the voltage. i.e. P = I x V.
Extensions
• There is one other term that is used in DC circuits, but it is not needed for most simple
experiments. That is resistance (R). Resistance is simply a measure of how hard it is
to get the electrons to move through a particular component. The best way to show
this (though easier in words than practice) is to have the students imagine repeating
the above activity underwater. After a little thought they should be able to see that you
would have to throw the balls much harder to get them to the bulb with the same
energy they had in air and that it would be hard to keep them coming as fast. That is,
the water has a higher 'resistance' than the air.
• If your students are having trouble with analyzing circuits have them act out the
proposed circuit using balls as above. The only 'extra' idea needed is that electrons
can only travel through wires, that is, you can only throw the balls to certain people.
One way to implement this would be to use yarn to show where the wires are, then you
can only throw the ball to someone to whom you are connected by yarn.
• Also, it would be better to represent the batteries by two people each, one for each
pole, one (the positive pole) can only catch the balls, the other can only throw.
• Other components can also be added. For instance a switch might be represented by
two people standing next to each other who can only pass the balls, not throw them, to
each other and only when they are holding hands (closed) not when they are
separated (open).
Visit suggestions:
Have your students try to build a circuit that:
•
•
•
•
•
contains a light that is on all of the time.
contains a light that can be switched on and off.
contains a buzzer that can be switched on and off (a buzzer that is on all of the time
is REALLY annoying).
contains both a light and a buzzer: Is it possible for the buzzer and the light to be
turned on simultaneously? (Why or why not?) Does switching the light-buzzer positions
change anything?
uses a tilt switch. (Look carefully and determine how the tilt switch works.)
Sources:
Hewitt, Paul G. Conceptual Physics, A High School Physics Program. Menlo Park, CA: Addison
Wesley Publishing Co., Inc., 1987.
Horowitz, Paul and Winfield Hill. The Art of Electronics. NY: Press Syndicate of the University
of Cambridge, 1985.
“Magnetism and Electricity.” Module Overview, Grades 3-4. Full Option Science System. U.C.
Regents, University of California, 1992.
Serway, Raymond, A. Physics for Scientists and Engineers with Modern Physics. 2nd ed.
Philadelphia: Saunders College Publishing, 1986.
Page 24
DIGITAL DRUMS
SOUND
Visitors play a set of eight digital drums after making a selection from a wallmounted panel of synthesized choices.
To record
and play your
voice:
MICRO
VOICE
PHONE
DRUMS TABLA* SOUND FX
PIANO STRINGS BASS SYMPHONY
1. Push and HOLD the ‘voice’
button to your right.
2. When the light is lit, speak
into the microphone above.
3. Play the drums!
drumheads
*tabla: a small hand drum of India (Source: “tabla.” The American Heritage Dictionary. 2nd
College Ed. Boston: Houghton Mifflin Co., 1982.)
Text Panel:
“I’m drummin’ up some science!”
“How does it work?”
“These ‘drums’ are sensors that tell a computer which notes to play. By picking a
different selection - even recording my own voice - I can make many sounds with
one instrument.”
“Since all sound can be digitally recorded as a series of ones and zeros - a
computer can recreate sounds by repeating numbers in a specific order.”
“Can you play a tune?!”
The BIG Idea: A listener is able to distinguish between similar tones (of the
same pitch, duration, and intensity) produced by different musical instruments
because of the tones’ “timbre.”
Sound is generated by vibrating objects. A sound is considered to be “noise”
when it is composed of irregular, incoherent vibrations. When a sound results
from an object vibrating at a regular, steady frequency, the sound that is produced
may be interpreted as a musical tone.
When struck, an object will naturally vibrate at a characteristic frequency known
as its fundamental frequency.
Page 25
DIGITAL DRUMS
SOUND
The pitch (highness / lowness) of a tone
depends on the vibrating object’s
fundamental frequency. Fast moving,
high frequency vibrations generate high
tones. Slower, low frequency vibrations
generate lower tones.
Electronic frequency generators are able
to produce pure tones, each consisting of
a single, fundamental frequency. If all
musical instruments generated pure
tones, a listener would be unable to
distinguish between one instrument and
another. However, objects may vibrate at
more than one frequency at a time.
Example: A violin string fixed at both
ends, would naturally vibrate at the
following frequencies:
fundamental frequency
Musical instruments produce composite
sounds with overtones superimposed on
the fundamental frequencies. For any
given tone, different types of instruments
produce different numbers of overtones
(also known as harmonics). Overtones
correspond to multiples of the
fundamental frequency.
While generated at the same time,
overtones are produced at a much lower
volume than the fundamentals.
Nevertheless, the overtones are
responsible for the timbre (also known as
“tone color” or “quality”) of the tone
emitted by an instrument. One way that
listeners can differentiate between
instruments is by recognizing the distinctive timbres.
1st Overtone
2nd Overtone
3rd Overtone
Sounds produced by instruments of a single type may also vary because of
differences in material and construction.
A single tone is comprised of several parts. Each individual tone has a beginning
attack section, a sustained middle section, and an ending decay section. The
initial part of the sound, the attack, may rapidly change with respect to amplitude
and overtones. The characteristics of the sustained section of the tone remain
fairly constant. The tone’s decay may be abrupt or gradual. In general, tones also
differ in their intensities and duration.
Page 26
DIGITAL DRUMS
SOUND
Try this at school:
Web site Synthesizer
http://library.thinkquest.org/19537/Main.html
(Source: Kulesza, Alex, et al. “The Soundry.” A ThinkQuest ’98 entry. (9/18/2000).)
Description: The web site listed above provides interactive online experiments dealing
with sound. One of the interactive experiments:
http://library.thinkquest.org/19537/cgi-bin/showharm.cgi
focuses on harmonics
(overtones). The user is able to vary the harmonics of a sound, see the corresponding
wave patterns and hear the results. To demonstrate the difference in timbre between a
clarinet and a trumpet, click on the name of each instrument and listen to the differences.
This is what the user sees on the screen:
Interactive Sound Lab
Harmonic Applet
S
O
U
N
D
R
E
S
E
T
1 2 3 4 5 6 7 8 9 10
Pre-Defined
Instruments
CLARINET
TRUMPET
Tunes
Harmonics
Instructions:
The Harmonics Applet allows you to play with harmonics to produce instrument sounds
similar to the sounds real instruments make. This applet takes the place of an electric
synthesizer. The only difference is that you make the sounds! You can also play songs
with the instruments you have made!
Follow these steps to understand how to use the Harmonics Applet:
1. Click on one of the Pre-Recorded Instrument Sounds that you are familiar with.
2. Notice how the sliders are positioned on each harmonic.
3. Click on the “Sound” button and listen to the synthesized sound of this instrument.
4. Now choose one of the songs and listen to the instrument again.
Press the “Reset” button to bring all the harmonics back to zero. Now, you can start
playing with the harmonics by yourself. To do this, click and hold on one of the sliders
and move it up and down along the harmonic bar. When you decide where to put the
slider just let go of the mouse button and move to the next harmonic. First, you might
want to try to copy the harmonics from the instrument you just heard. Then, when you
think you’ve mastered moving the sliders on the harmonics, create your own instrument!
By playing with the controls, you will be able to create and shape your wave any way you
like it. For example, you can create an approximation of a square wave by setting all of
the even harmonics to zero and setting the odd ones at decreasing levels. Experiment
and see what other types of waves you can make. Who knows? Maybe you’ll stumble
upon the sound of another instrument or make a new instrument sound altogether! If you
like what you’ve created, click “Post It!” to share it with others on our message board.
Page 27
DIGITAL DRUMS
SOUND
Visit suggestions:
Have your students experiment with the Digital Drums, paying close attention to:
•
•
•
•
the difference in timbre between the drums, tabla, piano, and bass choices. Can they
describe how the sounds differ from each other?
how their recorded voices are modified by the equipment. When a voice is recorded,
hitting each drumhead yields a different result. What characteristic(s) of the recorded
voice differ from one drum to the next?
the differences between the “SOUND FX” sounds and those heard when the
instrumental choices are selected. How are “everyday” sounds related to musical
tones?
the differences between digital drums and “regular” drums.
(On a “real” drum, hitting the drumhead with more force would yield a louder sound than
would a light tap. These drums do not transmit sound via vibration of the drumhead.
Rather, they are pressure sensors that function as on/off switches for the underlying
electronic equipment.)
Sources:
Apel, Willi, and Ralph T. Daniel. The Harvard Brief Dictionary of Music. New York: Pocket
Books, 1961.
Heckroth, Jim. “Tutorial on MIDI and Music Synthesis.” Harmony Central. ©1995 MIDI
Manufacturers Association. P.O. Box 3173, La Habra, CA 90632.
http://www.harmony-central.com/MIDI/Doc/tutorial.html
“music synthesizer.” Encyclopædia Britannica. Encyclopædia Britannica Inc., 1999-2000.
http://www.britanica.com
(Note: Site now requires a subscription to view full articles. 6/03)
“Musical Instruments.” Microsoft® Encarta® Online Encyclopedia. 2000.
http://encarta.msn.com
“Re: Can I recognize from sound Fourier spectrum a musical instrument?” The MAD Scientist
Network. ©1995-2000.
http://madsci.wustl.edu/posts/archives/oct98/905894507.Ph.r.html
“Re: Relationship of speed or sound, frequency and wavelength.” The MAD Scientist Network.
©1995-2000.
http://madsci.wustl.edu/posts/archives/feb98/885616068.Ph.r.html
Page 28
DOMINO STATION
MECHANICS
Visitors witness the domino effect firsthand by setting up long pathways of
oversized dominoes and then knocking them down.
Text Panel:
“Here’s a riddle for you: How are dominoes like the ocean?”
When you make a path and knock ‘em down, you’re seeing the energy move in a
wave. That’s the same way water molecules make a wave on the ocean -”
“- or air molecules make a sound wave reach your ears!”
“Molecules in a solid are closer together. This moves the wave faster. Try
varying the spacing in your domino ‘molecules’.”
The BIG Idea: When a longitudinal wave travels through a medium, the
molecules in the medium transfer the energy pulse from one place to another but
remain in essentially the same location.
Longitudinal compression waves, such as sound or water waves, travel by
transferring energy from molecule to molecule. A sound generated by the
vibration of an object, is transferred through the air as follows (see diagram):
•
An object is acted upon such that it begins to vibrate.
•
The object moves inward, leaving a larger space for the closest air molecules
to occupy, creating an area of rarefaction (lower air pressure).
•
The object moves outward, pushing the closest air molecules together,
creating an area of condensation (higher air pressure).
•
One condensation-rarefaction pulse is referred to as a sound wave.
The drumstick strikes
the drumhead.
The drumhead
moves inward and
the air molecules
closest to its
surface have room
to spread apart.
The drumhead
moves outward and
the air molecules
closest to its surface
move closer
together.
Note that the molecules bump into each other, transferring the energy of the wave through the
air. They do not, however, move far from their original position (circled areas above).
To understand why sound waves travel faster in a liquid than in a gas and faster in
a solid than in a liquid, consider the example on the following page.
•
The farther apart the molecules are, the longer it takes for an energy pulse to
be transmitted through a medium. Therefore, in general, sound waves travel
more quickly in solids than in liquids and more quickly in liquids than in gases.
Page 29
DOMINO STATION
MECHANICS
Molecules in a SOLID
object are packed closely
together.
Energy pulse
Molecules in a LIQUID
medium are farther apart
than they are in a solid
object.
Energy
pulse
Molecules in a GAS tend to
be located farther apart than
they are in a liquid.
Energy
pulse
Try this at school:
How Would the Speed of Sound Be Affected Through Different Media?
(Source: Hartshorn, Robert L., et al., see citation below.)
Materials: Approximately 100 dominoes
Procedure
• Line up dominoes at evenly spaced intervals (approximately 2 cm apart stretching out
over a 100cm length). Push over the first one and watch this disturbance transmitted
to the next domino, and to the next, etc. Measure the amount of time it takes until the
last domino topples. Let’s say this setup represents sound being transmitted through a
solid.
• Now line up the dominoes at evenly spaced intervals (approximately 4cm apart)
stretching out over a 100cm length. Push the first domino and predict whether the time
required for the last domino to topple will be greater or smaller than in the first case.
[Longer] This might represent a liquid where the molecules are farther apart.
• Setting up both the solid and liquid situations and applying the disturbance at the
same time may more graphically illustrate the comparison. Sound travels slower
through substances where the particles making up the medium are farther apart.
The general rule is that the speed of sound is directly proportional to the density of
the medium.
Visit suggestions:
Have your students repeat the experiment described in the section above.
•
•
•
•
•
•
•
Divide the students into two groups.
Give each group an equal number of dominoes.
Designate one group to be “Solid” and one group to be “Liquid”.
Have the Solid group set their dominoes up close together in a line.
Have the Liquid group set their dominoes up in a line, spaced further apart than the
Solid group’s dominoes.
When both lines are complete, simultaneously knock down the first domino in each
line.
Which line falls more quickly? Why? How can this information be applied to the
movement of a sound wave?
Sources:
Hartshorn, Robert L., et al. “How Fast Do Dominoes Fall?” Physical Science Activities Manual.
Center of Excellence for Science and Mathematics Education at The University of Tennessee at
Martin, Martin, TN, 1994.
http://cesme.utm.edu/resources/Science/PSAM.html
Page 30
LASER HARP
LIGHT
Visitors play a stringless harp by blocking a
series of laser beams set in a harp
framework. As each beam is broken, an
electronic switch is tripped, resulting in a
single tone.
CAUTION:
LASER
DO NOT
STARE UP
INTO
BEAM
Text Panel:
“Look! I’m making music - with no strings attached!”
“The strings have been replaced by laser beams and sensors that ‘see’ light.
When you block the beam, a sensor tells the computer to play the note.”
“People use lasers everyday in everything from CD players to grocery store
scanners to eye surgery!”
“Can you play a tune?!”
The BIG Idea: The characteristics of laser light, particularly the fact that a laser
beam remains narrow even at a great distance from its source, make this type of
light ideal for use in switching circuits.
Each of the eight harp “strings” consists of two parts.
At the top of the harp’s frame are eight small lasers.
At the bottom of the harp’s frame are eight
corresponding phototransistors that detect the beams.
If any beam is blocked so that it does not make
contact with its corresponding detector, the circuit
connected to the detector is triggered and a tone
sounds.
Laser
Detector
Page 31
LASER HARP
LIGHT
Laser beams have certain characteristics that make them ideal for this kind of
circuitry. Laser light differs from ordinary, white light in three basic ways.
1. Wavelength
Laser light is monochromatic.
This means that it is composed
of one wavelength of light.
White light can be broken down into the
entire visible light spectrum because it is
composed of all visible wavelengths of light.
2. Coherence
Laser light is coherent. This means that
all of the light waves are in phase with
one another and are moving in the same
direction.
White light is incoherent. The light waves
interfere with each other because they are
not in phase and are moving in many
directions.
3. Dispersal
A laser beam remains narrow, even at a
great distance from the source.
A beam of white light disperses
(spreads out) as it moves away from
the source.
Because laser beams do not disperse as they move away from their sources, they
can be accurately focused on small targets (such as the phototransistors in this
exhibit).
Page 32
LASER HARP
LIGHT
Try this at school:
Investigate the differences between white light and laser beams
Materials
• Flashlight
• Cardboard
• Scissors / utility knife
• Masking tape
• Paper
• Prism
• Blackboard/ chalk or Whiteboard/ dry-erase marker or paper taped to the wall and a
regular marker
Procedure
• Using the cardboard, knife, and tape, create a cover for the bulb end of the flashlight
such that the light exits only through a very small hole.
Investigate wavelength composition
• In a dark room, shine the occluded flashlight beam through a
prism.
• Observe the refraction (bending of rays) of white light.
• Repeat with the laser pointer.
Note: To see the actual beams, use a plant-mister / spray bottle to spray water mist
along the beam paths.
Investigate dispersion
• From a distance of approximately 10 ft away, shine the flashlight onto the blackboard /
whiteboard/ paper and trace around the outer edge of the light circle.
• Repeat using the laser pointer.
Visit suggestions:
Have your students experiment with the Laser Harp, paying attention to the following:
•
•
•
•
Why can’t the laser beams be seen in between their sources and detectors?
Why is it that the beams can’t be seen, yet blocking their invisible paths trigger the
tones?
Do the eight electronic circuits connected to the detectors work independently? Can
more than one note be triggered at the same time?
A real harp offers the player the opportunity to vary the dynamics (loudness /
softness) of the tones depending on how hard the strings are plucked. Is it possible to
vary the dynamics of the Laser Harp tones?
Sources:
Page 33
MARBLEWORKS®
Visitors use MarbleWorks®
pieces to construct elaborate
tracks for marbles.
MECHANICS
Note: MarbleWorks is located in the Structures Station
area. Building materials in this area are rotated on and
off the floor every four months. If you are interested in
using MarbleWorks during your visit, please call
ahead to check on its availability.
Text Panel:
“Rollin’, rollin’, rollin’; keep them marbles rollin’...”
“As gravity moves the marble downhill, the potential energy it has is released as
kinetic energy - the energy of motion.”
“This energy can be harnessed to do work - turning paddle wheels or speeding
the marble along a pathway.”
“A moving roller coaster car, the water pouring over a turbine blade or a
baseball in flight all have kinetic energy.”
The BIG Idea: Potential energy is the energy stored in an object above the
ground. Kinetic energy is energy of motion. The potential and kinetic energy of
an object (in an ideal mechanical system) are proportional: when one increases the
other decreases.
Energy is the ability to do work. There are two different basic forms of
mechanical energy: potential and kinetic.
•
Potential energy, PE, is the energy stored in an object by virtue of its position.
An object with potential energy is in its current state because work has already
been applied to it. This energy may be changed into kinetic energy.
•
Gravitational potential energy, PEg, is the potential energy stored in an object
because it is at some height above the earth’s surface. PEg = mgh where m is
the mass of the object, g is the acceleration of gravity, and h is the height of the
object above the earth’s surface. Note that mg is equal to the weight of the
object.
•
Kinetic energy, KE, is the energy of motion. KE = ½ mv2 where m is the
mass of the object and v is the object’s velocity.
•
Energy is always conserved. This means that it may change from one form to
another, but the total energy of a system is always the same.
Total Mechanical Energy of the System = PEg + KE
When a marble is placed at the top of a MarbleWorks® track, the visitor has done
work on it (to lift it up) and the marble now has the potential to do work. This
potential energy is “stored” in the marble. When it is placed at the top of the
structure, the marble’s energy is 100% potential and 0% kinetic. As the marble
rolls downward, the potential energy decreases as the kinetic energy increases.
Page 34
MARBLEWORKS®
MECHANICS
The moment when it reaches the floor, the speeding
marble’s energy is 0% potential and 100% kinetic.
100% PEg
IN
0% KE
Note: The above describes the “ideal” case where
there are no “losses” involved. The marble actually
loses a very small amount of energy between the top
and bottom of the track. These losses may result from
friction between the marble and the track, noise
resulting from the marble hitting the plastic track’s
walls, etc. However, the energy itself is not lost (it is
always conserved). Rather, it has changed into other
forms – heat, in the case of friction, and sound, in the
case of noise.
0% PEg
100% KE
Try this at school:
OUT
Potential & Kinetic Energy
http://www.educationplanet.com/lessonplanet/search/redirect?id=615&mfcount=8&mfkw=marbles
(Source: Pflugrad, Ben. “Potential and Kinetic Energy.” Education Planet Lesson Plans. (9/18/2000)
Note: Site now requires a paid subscription to access this lesson plan 6/03).
Description: This lesson is to help students more fully understand the relationship
between Potential and Kinetic energy. Students should already know the definitions for
work and mechanical energy.
Grade Level: 5-6
Materials
• 3 marbles (different sizes/ weights)
• Inclined plane
• Metric ruler
• Milk carton
Procedure
• Set up a demonstration of rolling three different sized marbles down an inclined plane.
Place the bottom section of a milk carton at the bottom of the ramp to catch the marble
and measure the distance that it moves the carton.
•
1.
2.
3.
4.
Ask questions below before the demonstration:
Who can tell me the meaning of work?
What is mechanical energy?
Which marble has more mechanical energy (if all were sitting on a flat plane)?
If I put the marbles up on the inclined plane, would they have energy? Why?
(This energy is called potential energy (PE), energy at the point of release, or stored
energy. The energy of a moving object is kinetic energy (KE). PE changes to KE as the
marble rolls down the ramp.)
5. Which marble do you think has the most PE?
•
Ask students to predict how many centimeters each marble will move the milk carton,
and which marble will move it the most. (write on a piece of paper)
Page 35
MARBLEWORKS®
•
•
•
•
MECHANICS
Demonstrate using one marble and record the distance the milk carton was moved.
Repeat five times and take the average distance. Demonstrate using the second and
third marbles using the same process.
Compare students’ predictions with outcomes.
Which marble had the most energy? Why?
What would happen if the smaller marble were let go at twice the height of the larger
one? Why? (Demonstrate)
Extensions
• What are some examples of storing and using energy in our environment? (Teetertotter, Wrecking ball, Hydroelectric dam, Elevators)
• What factors affect the amount of work an object can do? (Mass and Height)
• On the paper that students wrote their predictions, have them explain why their
predictions were right or wrong.
Visit suggestions:
Have your students try the following:
•
•
•
Build the tallest track they can reach while standing on the floor.
Build a track with multiple pathways.
Build a track using all the MarbleWorks® pieces.
Sources:
Eby, Denise, and Robert B. Horton. Physical Science. New York: Macmillan Publishing
Company, 1986.
Page 36
MOBILE STATION
MECHANICS
Visitors create a mobile using foam shapes and metal
hooks. The mobile is suspended such that it may be raised
and lowered at the touch of a button for easy access by
smaller visitors.
Text Panel:
“It’s art!”
“It’s science!”
“I’m making a mobile by balancing shapes on these blue levers.”
“The place where each lever tilts is called the fulcrum. The location of the
fulcrum is different on some of these levers.”
“That means the weight it needs on each side is different, instead of equal. When
the lever balances, it has equilibrium.”
“You on a see-saw, a flamingo on one leg, or a person with a crutch all use
balance.”
The BIG Idea: A mobile is a system of balanced levers.
A lever consists of a rigid beam and a fulcrum (pivot point). The mobiles
constructed at the Mobile Station are first-class levers. (See all three classes of
levers on the following page.)
In order for a first-class lever to balance, F1 x d1 = F2 x d2
where F1 and F2 are the forces applied to the lever by masses
m1 and m2 (these forces are assumed to be perpendicular to
the lever) and d1 and d2 are the distances from the fulcrum to
the places where F1 and F2 are applied.
m1
•
In the case of the mobile at the Mobile Station, the
distances d1 and d2 are fixed and equal. Therefore, the only
variables that may be changed are F1 and F2, the forces
applied to the lever by the masses m1 and m2.
fulcrum
d1
d2
m2
F1
F2
nd
Newton’s 2 Law may be written: F = ma where F is the force
applied by mass m, and a is the acceleration of mass m. Once the shapes are
hooked onto the mobile, their acceleration is equal to that of gravity, g. Thus, F =
mg where F is the force exerted by the earth’s gravity on an object. This force is
defined to be the weight of the object. Therefore, forces F1 and F2 are the
weights of m1 and m2.
•
The governing equation for a balanced mobile at the Mobile Station becomes:
Page 37
MOBILE STATION
MECHANICS
(total weight of m1) x d1 = (total weight of m2) x d2
Note that (total weight of m1) equals the summed weights of all objects hanging
at a distance d1 from the fulcrum and similarly, (total weight of m2) equals the
summed weights of all objects hanging at a distance d2 from the fulcrum.
Classes of Levers
A first-class lever is one in which
the fulcrum (pivot point) is
placed between the load and the
point where the effort is applied.
A second-class lever (e.g.
wheelbarrow) is one in which the
fulcrum is at one end of the bar,
the effort is applied at the other
end, and the load is in-between.
A third-class lever (e.g. hammer)
is one in which the fulcrum is at
one end of the bar, the load is at
the other end, and the effort is
applied between the two.
first-class lever
m1
d1
load
d2
fulcrum
F1
m2
F2
effort
m1
second-class lever
fulcrum
load
effort
fulcrum
third-class lever
load
effort
Try this at school:
The Art of Physics
(Source: Franklin, Carl E. and Sandra J. Rhoades. “The Art of Physics: Mobile-ize your students
with this interdisciplinary project.” The Science Teacher. March 1989: 65-66.)
Description: Mobile-ize your students with this interdisciplinary project.
In searching for new methods to make physics both useful and fun for our students, we
developed a project that makes use of concepts students have learned previously and
features the added advantage of being interdisciplinary. Following a study of torques,
usually in November at our school, the teacher assigns the construction of mobiles to the
class. The mobiles could be useful for any discipline, since replicas of cells or biological
organisms could be substituted for the objects. Biology students, of course, may not
know about torque. The mobile project also promotes the idea that science is a creative
process, something that many students do not realize.
In teams of two or three, the students both design and construct a mobile for display in
the physics classroom, doing some of the work at home and some of the planning and
construction during lab periods. In order to maintain the scientific integrity of the project,
the teams first design the mobile on paper, calculating the clockwise and
counterclockwise torques on each arm, and then they determine the position of the
supporting strings using the following equation:
τ = rF
where F equals force (weight) in Newtons, r equals length of lever arm in meters, and τ
equals torque in meter-Newtons. To differentiate between energy units of joules, which
Page 38
MOBILE STATION
MECHANICS
are represented by N•m, we give torque units in m•N. Students submit this blueprint of
the mobile to the teacher before construction begins to ensure that the elements of the
mobile are not arranged by trial and error but according to a calculated design. The
copyable instructions on the page following this section which we hand out to the
students, list the requirements of the project.
Before the project begins, we notify the students that we will score the mobiles at the
level of a major test, with each of the following factors having a value of 25 points:
•
•
•
•
Design. The sketch, blueprint, and finished mobile will be evaluated for consistency,
sound planning, and quality of execution.
Calculations. Each arm of the mobile should be labeled on the blueprint. The position
of the strings, length of the dowels, and mass of each hanging element should be
included. Any difference in the calculated and real position of any support string
should be noted with relative error calculated.
Artistic merit. A member of the Art Department will award the points in this area,
based on sound design and general artistic merit.
Helpful Hints. This list, which the student compiles, should be clear and concise and
will serve as the conclusion for the project. A sample list appears on the page
following this section. We assigned the Helpful Hints list because we found that
although several mobiles were beautifully conceived and carefully designed, they
would not hang properly or they broke while hanging – despite the fact that the
students who made them had worked hard and learned much. By pinpointing some
possible sources of error, the students could be awarded the credit their efforts
merited.
At Westminster High School, we are fortunate to have a colleague, Tad Mollenkamp, who
teaches art and is a former science teacher. We asked him to introduce our physics
classes to some basic concepts of good design. He gave them a brief background on the
work of Alexander Calder, who combined engineering training with art to become the
pioneer of the mobile. Tad showed slides of several of Calder’s works, including the 26m wide mobile that is suspended in the East Wing of the National Gallery of Art.
Because of his science background, Tad was able to integrate scientific principles with
artistic methods. He stressed that the students should strive for interest in their designs.
He both impressed upon them the visual impact of mass and encouraged them to be
aware of the center.
We have assigned this project for several years with gratifying success. It is an example
of visible physics and attracts favorable attention from students and faculty who pass by
our classrooms. Since there is not enough room to hang all of the mobiles in our three
physics labs, we display mobiles in the principal’s office, the hallways, and the faculty
lounge, adding to increased positive public relations for physics.
The mobiles have been focused on varied themes and have called for a wide variety of
suspended objects, such as rockets, records, theatrical masks, toys, electrical
equipment, sporting equipment, and Christmas ornaments.
The project helps to emphasize the idea that physics is something that not only happens
in a laboratory, but also applies to other disciplines, and even to other areas of our lives.
The project gives students a feel for the problems and challenges faced by architects and
design engineers who must develop structures and objects that are visually pleasing and
technically sound. The students discover that calculations and planning are essential for
the success of the mobiles. And they find, once again, that physics is fun.
Page 39
MOBILE STATION
MECHANICS
Carl E. Franklin is the co-chair of the science department and also teaches physics at Westminster
High School, 1424 W. Paces Ferry Rd., NW, Atlanta, GA 30327. Sandra J. Rhoades is a member
of the Physics Teaching Resource Agent program of the American Association of Physics
Teachers and the education director of the Science and Technology Museum of Atlanta, 395
Piedmont Ave., NE, Atlanta, GA 30308.
Biography of Alexander Calder: Excerpts from Calder Curriculum (see citation below)
Alexander “Sandy” Calder was born into a family of renowned artists who encouraged
him to create from a very young age. As a boy, he had his own workshop where he made
toys for himself and his sister. He received a degree in mechanical engineering in 1919
but soon after decided to pursue a career as an artist. Calder attended classes at the Art
Students League in New York from 1923 to 1926, supporting himself by working as an
illustrator.
In 1926 Calder arrived in Paris where he developed his Cirque Calder, a work of
performance art employing small-scale circus figures he sculpted from wire, wood, cloth,
and other materials. Through these elaborate performances, Calder met members of the
Parisian avant-garde. At the same time, Calder sculpted three-dimensional figurative
works using continuous lengths of wire, which critics described as drawings in space. He
explored ways to sculpt volume without mass and captured the essence of his subject
through an economy of line and articulated movement. Calder’s wire works then became
increasingly gestural, implying motion. By the end of 1930, this direction yielded his first
purely abstract sculptures.
After translating drawing into three dimensions, Calder envisioned putting paintings into
motion. He developed constructions of abstract shapes that can shift and change the
composition as the elements respond to air currents. These sculptures of wire and sheet
metal (or other materials) are called "mobiles." A mobile laid flat exists only as a skeleton,
a reminder of its possibilities, but when suspended it seems to come alive.
Calder also developed “stabiles,” static sculptures that suggest volume in multiple flat
planes, as well as standing mobiles, in which a mobile is balanced on top of a stabile.
Calder furthered his work by developing a monumental scale. His later objects were huge
sculptures of arching lines and graceful abstract shapes that now inhabit public plazas
worldwide.
Alexander Calder, “Blue Feather,” standing
mobile, sheet metal, wire and paint, 42” x 55” x
18”, Calder Foundation, c. 1948. Æ
Å Alexander Calder, mobile, steel plate, rods
and paint, 300” x 540” x 204”, The Port Authority
of New York and New Jersey, 1957.
Source: Calder Curriculum. Calder Foundation Education Materials. (9/11/2000).
http://www.calder.org
Page 40
MOBILE STATION
MECHANICS
Visit suggestions:
At the Mobile Station have your students try the following:
Determine the relative weights of the foam shapes:
•
Use the blue lever as a balance scale Æ
•
Using the small, medium, and large circles, squares, and triangles, how many ways
are there to fill in the blanks in the following equations?
1) ___ + ___ = ___
e.g.
+
2) ___ + ___ = ___ + ___
=
Sources:
“ See-Saw Physics Teacher’s Guide.” Playground Physics.
http://lyra.colorado.edu/sbo/mary/play/levert.html
Page 41
MOBILE STATION
MECHANICS
The Mobile Project
Objective
Design and construct a mobile that will fit into a 1m by 1m by 1m space.
Procedure
• The mobile should have a minimum of three freely swinging arms as well as a general
theme to enhance design merit.
• Select the hanging items of the mobile. Plan to use 3/16-in. to 1/2-in. wooden dowels
as arms. Dowels are available in standard inch increments at hardware stores or
lumberyards. The size of the dowels will be determined by the weight of the elements.
• Sketch the general plan of the mobile on graph paper using a scale of 1 cm for every
10 cm. The sketch should provide an idea of how the mobile will look within the 1-m3
limitation. Determine the approximate length of each arm on the sketch.
• Find the mass of each element. You might want to record the mass of each item on
masking tape and attach the tape to the item.
• Calculate the position of the support string on each arm. You will achieve the best
results by starting with the lowest arm and working upward. Since it is difficult to tie
string to the very end of the dowel, leave a 0.3 cm space at the end of the dowel in
your planning and calculations, and then make a notch in the dowel for each string so
that it will not slip.
Support String
•
•
•
•
Make a blueprint of the mobile indicating the real lengths and positions of all strings,
and show all masses, using the scale that you used previously.
Using the blueprint, design and construct the mobile. Then hang it in the classroom
by the specified date.
Make a list of helpful hints for next year’s students.
Submit your sketch, design blueprint, calculations, and list of hints by the due date.
Sample helpful hints
•
•
•
•
•
•
•
•
•
•
•
•
•
Use light objects.
Make the mobile simple but big, in other words, visually strong.
Plan ahead! Calculate carefully and accurately.
Do not take the easy way out. Make the mobile look attractive and add details, no
matter how small.
Bring extra supplies to repair the mobile once it is up, in case something happens to it.
Be creative. Use a single theme, but use something you like.
Fishing swivels can be used to attach elements for added mobility.
Fishing line looks more attractive than string but is more difficult to knot.
Attach your strings with tape; when you are sure of their placement, make the notches
in the dowel.
Do not use fragile items on your mobile.
Do not use too many objects – it is difficult to balance them visually.
Don’t panic. You will get it done.
Don’t ever give up. Take time to work on it. It takes time to figure everything out.
Page 42
NEWTON’S CRADLE
MOMENTUM
Visitors experiment with this larger-than-average
desktop toy by varying the material properties of the 5
aligned, swinging balls. Each suspended ball may be
removed and replaced with a sphere of the same size.
However, not all balls are made of the same material.
Text Panel:
“Put on five of the same balls, then let one of the end balls swing into the others.”
“When the ball on the end hits the others, its momentum is transferred through
the others, knocking the opposite end ball away.”
“You can see this same effect in bowling, in a game of pool ... or in a multi-car
collision on the highway!”
“Ouch! What if you mix the balls? Can you see how different materials changes
the result?”
The BIG Idea: In any collision, momentum is always conserved. Some
collisions are elastic and some are inelastic.
The linear momentum, p, of an object of mass m, is defined to be
p = mv
where m is the mass of the object and v is its velocity.
•
The momentum in a closed system is ALWAYS conserved. This means that
the total momentum before a collision between two objects is the same as the
total momentum after the collision. After the collision each object does not
necessarily continue to move in its initial direction or with its initial velocity,
but the total momentum of the system is the same -- only redistributed.
There are several different types of collisions. In ALL of the following cases, the
initial momentum of object #1 added to the initial momentum of the object #2
equals the final momentum of the object #1 added to the final momentum of
object #2.
mv#1 initial + mv#2 initial = mv#1 final + mv#2 final
Page 43
NEWTON’S CRADLE
•
MOMENTUM
An elastic collision is one in which the colliding objects’ total momentum
AND total kinetic energy are conserved.
T IME
2 objects of equal mass
collide head on
m2
m1
2 objects of equal mass,
1 object at rest
m1
m2
Elastic collision
Elastic collision
•
•
both objects are moving in the same
direction at different velocities
m1
m2
Elastic collision
An inelastic collision is one in which the colliding objects’ total momentum is
conserved, but the total kinetic energy of the system is not. In this type of
collision, the kinetic energy of the colliding objects may be “lost” to the
creation of heat, object deformation, or noise.
A perfectly inelastic collision is one in which the colliding objects stick
together at impact. This implies that the two objects have the same final
velocity.
2 objects of equal mass
collide head on
m2
m1
T IME
Perfectly inelastic collision
1 object at rest
m1
m2
both objects are moving in the same
direction at different velocities
m1
m2
Home Demo #17 Marble Madness
http://nyelabs.com
(Source: “Marble Madness.” Home Demos. BillNye.com)
Description: This simple experiment will give you a chance to prove to yourself that when
it comes to physics, "Every action has an equal but opposite reaction." It will also give
you the opportunity to lose your marbles, so try to keep track of them.
Materials
• Ruler with a center groove
• Seven marbles, each the same size
Procedure
• Tape the ruler to a level surface.
• Place five marbles in a row touching each other in the center groove of the ruler.
• Roll a sixth marble down the groove into the marbles standing still.
• Repeat the experiment, but this time roll two marbles into the row of five.
What's Happening?
When a moving marble hits the row of motionless marbles an exchange of energy takes
place. The rolling marbles have momentum, which is transferred from one marble to the
next, until the marble (or marbles) at the other end gets sent into motion.
Page 44
NEWTON’S CRADLE
MOMENTUM
Whelmer #22: Energy Transfer
(Source: Jacobs, Steven.
1997.)
“Energy Transfer.”
Whelmers. McREL Accessible Science Series,
Description: A ping pong ball bounces 10 to 15 feet high using energy transferred from a
golf ball.
Materials
• Golf ball
• Ping-pong ball
• Hard floor surface
• Clear plastic tube(optional) with a diameter slightly larger than
that of a golf ball
• Tape (optional)
Instructions
This activity requires some manual dexterity. Practice each step before presenting it to
students.
• Hold the ping-pong ball chest high and release it. Note how high it bounces. Hold a
golf ball chest high and release it. Note how high it bounces. Hold both in one hand
with the ping-pong ball positioned on top of the golf ball. Release both. The ping-pong
ball bounces much higher than it did when dropped alone. The golf ball bounces lower.
• The balls must be dropped vertically, with the ping-pong ball directly over the golf ball.
Until you have mastered the technique of releasing both balls simultaneously, the pingpong ball will bounce off at an angle. When dropped properly, the ping-pong ball will
shoot straight up, 10 to 15 feet.
Presentation:
• This activity works best on a concrete or hard tile floor. A large concrete block can be
placed on a carpeted floor. The presenter should be positioned so that students can
observe the height of each bounce of the balls.
• Before dropping either of the balls, ask students to predict how high each will bounce.
Use tape on the wall behind the presenter to mark the height of each bounce.
• After the initial drop of the ping-pong ball, ask students how the ball can be made to
bounce higher (throw the ball down, drop it from a higher point, etc.). Relate that each
response is an example of adding more energy to the ping-pong ball.
• Suggest to students that you will transfer energy from the golf ball to the ping-pong
ball. Ask them if they think it is possible to transfer energy from one thing to another.
Ask for examples (kicking a soccer ball, hammering a nail, etc.).
• Ask students to explain where the energy came from that caused the ping-pong ball to
bounce so high. (golf ball)
• Ask them to explain what must have happened to the golf ball if it did transfer some of
its energy to the ping-pong ball. (bounced lower than before)
• Did any of them observe the lower bounce of the golf ball during the first test? (most
follow the more interesting flight of the ping-pong ball) Relate to students that scientists
must learn to be keenly observant.
• Direct them to make careful observations and measurements as you repeatedly drop
both balls. Use tape strips to indicate the height of different bounces.
• If the presenter has great difficulty dropping both balls free hand, a plastic tube can be
used. Select a tube that is slightly larger in diameter than the balls. Drop both balls in
the top of the vertical tube. A similar bouncing effect can be observed. Tape markers
can be applied to the outside of the tube to indicate bounce height.
Content
This activity is a good example of one of the basic laws of physics;
the Conservation of Momentum. Momentum is described by the formula M = m x v. (M is
momentum; m is mass; v is velocity) In the collision of the golf ball with the ping-pong
Page 45
NEWTON’S CRADLE
MOMENTUM
ball; m(g) x v(g) = m(pp) x v(pp). The mass of the golf ball is much greater than the mass
of the ping-pong ball. In order for momentum to be conserved (the equation to be
balanced), the velocity of the ping-pong ball will be much greater. Students experience
conservation of momentum with a baseball and bat. The much more massive bat imparts
a greater velocity on the baseball.
Extensions
• Collect balls of various sizes and masses (e.g. baseballs, large ball bearings, small
rubber balls and other ping-pong balls). Students should predict which ball will allow
the ping-pong ball to bounce higher when the activity is repeated. Repeat the activity
and compare the predictions to the outcomes.
• Older students should compare the concept of momentum to the mass and velocity of
the balls using the formula M = m x v in supporting their predictions and justifying the
outcomes.
Visit suggestions:
Have your students experiment using the Newton’s Cradle exhibit to determine what
happens to each individual ball when:
(A) All of the balls are the same and:
1
2
3
4
5
Step 1: Ball 1 is pulled back and released.
Step 2: Balls 1 and 2 are pulled back and released together.
Step 3: Balls 1,2 and 3 are pulled back and released together.
Step 4: Balls 1,2,3 and 4 are pulled back and released together.
What is the relationship between the number of balls released and the response of the
other (initially still) balls?
(B) Replace all 5 balls so that all of the balls are the same, but are made of a different
material from those in (A). Repeat Steps 1-4. Compare the results with the results
from (A).
Ball 1
Ball 2
Ball 3
Ball 4
Ball 5
X
X
X
X
♦
(C) Try different ball combinations
X
X
X
X
♦
as shown in the table at the right,
X
X
X
X
♦
where ♦ represents one material
(e.g. plastic) and X represents a
X
X
X
X
♦
second material (e.g. rubber).
X
X
X
X
♦
Repeat Steps 1-4. Compare the
X
X
X
♦
♦
results with the results from (A).
X
X
♦
♦
♦
Sources:
Company, 1986.
Page 46
PLUMB CRAZY
ENGINEERING AND DESIGN
ball enters here
Visitors attach Velcro®-backed PVC pipes
and connectors to a carpeted wall, creating
pathways for ping-pong balls. The holes in
the wall are paired, such that if the ball is
put into one hole, it exits the wall at a
different location.
Point
A
Velcro®-backed
labels are
available.
(Points A, B, C)
ball finishes here
Text Panel:
“Plumbing problems?”
“Nope. I’m arranging pieces of pipe so my ball will travel through the wall
passages, the pipes - even the air.”
“The ball can travel along different pathways. Designing a route that reaches
many places can be fun and challenging.”
“People who design pathways like roads or plumbing or computer circuit boards
must figure out how to move things from place to place.”
The BIG Idea: There is often more than one way to get from one point to
another.
The Nature of Problem Solving: In science and engineering fields, many
questions can be reduced down to a generic: Starting with this particular input,
how do I get the desired output? To solve the problem, a solution must be found
such that seemingly separate things become connected.
INPUT
?
OUTPUT
For example, the problem is: Find a way to get from “A” to “B”.
All of the following are possible solutions:
•
A
A
A
A
A
B
Solution 1
B
Solution 2
B
Solution 3
B
Solution 4
B
Often in science and engineering, there are many solutions that reach the same
answer. Some solutions may be simple; some may be technically difficult. Some
may be cost-prohibitive; some may not be socially or ethically appropriate or
politically acceptable. Most of the time there is more than one path that can be
taken to reach the same place.
Page 47
PLUMB CRAZY
In the example above, all four solutions meet the stated criteria. In a less abstract
situation, there may be restrictions that must be inferred from the context of the
problem or that have been unintentionally omitted.
•
For instance, if the problem were stated, “Build an oil pipeline from points A
to B,” finances would undoubtedly come into play. Solution 1 would probably
be the most acceptable because it uses the least amount of pipe.
•
This does not mean that finding Solutions 2, 3, and 4 was a useless exercise.
If after surveying the area it became clear that there were immovable structures
along the path, a different solution might become more appropriate.
Creativity and flexibility play important roles in science and engineering. Often,
to fill in the “?” box, one must think outside of it (as in Solution 4).
Visit suggestions:
Bring these materials with you: paper, pencils, stopwatch, Polaroid camera / film (if
available).
At Plumb Crazy, have your students try to find multiple solutions to a given problem.
Procedure
•
What is the objective? Before
attempting any experimentation, the
students should decide on a goal.
•
What are the initial conditions?
•
What are the constraints? Students
should then decide on a set of
restrictions.
Example
•
The ball will always finish in the cup.
•
•
•
•
•
What is already known?
•
•
How is success defined?
•
•
Find a solution.
Record the results.
•
•
•
Need more of a challenge? Add a
time constraint.
•
•
The ball may be placed in the hole at
Point A, B or C (students must designate
these holes).
Once the cup is in position, it may not
be moved.
No one may touch the ball once it is
placed in a hole.
There will be three separate paths,
each ending at the same place.
Thanks to gravity, the ball will roll
downward.
The ball will be placed in each of the
holes at Points A, B, and C twice, and
each time it will finish by landing in the
cup.
Try it.
Once the goal has been successfully
met, draw a diagram of the wall and the
pipe pathways (or take a picture).
Which pathway is the quickest? Have
a race and see. If you wish, try each
path individually and use a stopwatch to
record the finish times.
Sources:
Gardner, Martin. aha! Insight. New York: Scientific American, Inc., 1978.
Polya, George. Mathematical Discovery, On Understanding, Learning, and Teaching Problem
Solving. New York: John Wiley & Sons, Inc., 1981.
Page 48
POLYGONAPALOOZA
Visitors build structures using magnetic metallic rods and balls.
Text Panel:
“Where have all the polygon…?”
“A polygon is a flat closed shape made with straight edges - like a triangle or a
square.
Try making one using these pieces.”
“Now put a few triangles together to make a pyramid – you’ve just made a
polyhedron, a three-dimensional shape made of polygons.”
“If you look carefully at bridges and buildings, you’ll see that they are made out
of polygons too.”
The BIG Idea: Simple two-dimensional shapes can be put together to form
complex three-dimensional shapes.
A polygon is a two-dimensional closed shape with straight edges. The straightline segments that make up the polygon are called the sides. The
point where two sides of a polygon come together is called a
vertex. The number of vertices classifies the polygon.
A polygon is said to be “regular” if all of its sides are the same
length and all of its angles are of equal measure.
A solid object completely encloses a volume of space. A
solid made up only of planar (two-dimensional) faces, is
called a polyhedron. Each polygon making up the
polyhedron is called a face. The segments where two faces
come together are called the edges and the end-points of
these segments are called the vertices.
A polyhedron is said to be “regular” if it is made up of
regular polygons, all of the same size, and the same number
of edges meet at each vertex. It is only possible to construct
five Regular Polyhedra. This has been known since the
time of the Greeks, which is why these are known as the
“Platonic Solids.”
Page 49
vertex
side
Polygon
vertex
face
face
face
face
Polyhedron
edge
POLYGONAPALOOZA
The Five Regular Polyhedra
Face Shape
total #
of faces
# of faces at
each vertex
# of
vertices
total #
of edges
equilateral
triangles
4
3
4
6
equilateral
triangles
8
4
6
12
equilateral
triangles
squares
regular
pentagons
Regular Polyhedron formed:
tetrahedron
octahedron
icosahedron
20
5
12
30
6
3
8
12
hexahedron (cube)
dodecahedron
12
3
20
30
NOTE: While the metallic rods at this exhibit appear to be solid, each
rod is actually a hollow tube containing two separate magnets.
Because of the magnets’ random
magnet
orientations in the tubes, some rods will
have one end that is a magnetic North
N
pole and one that is a magnetic South
pole, some will have a magnetic North
N
pole at each end and some will have a
magnetic South pole at each end.
S
magnet
S
N
S
Try this at school:
Straw polyhedra and other nets
(Source: Department of Mathematical Sciences, New Mexico State University, last modified by Christopher
Moreno, 7/13/00. http://www.math.nmsu.edu/breakingaway/Lessons/straw/straw.html)
Straw polyhedra are skeletal polyhedra whose edges are non-bendable (8” long or less)
colored straws, held together by thin cotton twine threaded through the straws. Straw
polyhedra are very light and attractive looking, and they are a very valuable teaching help
in the early and middle grades.
Tools: In order to make straw polyhedra you need:
• Colored non-bendable plastic straws.
• Thin cotton twine (plenty of it), and scissors to cut it.
• A threading needle (bamboo skewers)
And a lot of "know how."
How to make and use a threading needle: Get bamboo skewers 10 or 11” long. Cut off
their sharp points with nail-clippers or scissors. With a sharp knife make a ½ to ¾” long
cut along the grain at one end. Push a piece of twine (near its end) across and
into the slit you have just made. The bamboo is elastic and will hold the twine quite well.
Your needle is ready for threading. You may use both ends of it, either pulling the twine
through a straw or pushing it through (in this case, the cut part of the bamboo needle
leads the way). After you finish, instead of pulling the twine out of the needle, cut it off,
leaving a small piece inside the slit. After you thread the needle the next time, pull out this
Page 50
POLYGONAPALOOZA
small piece. This makes threading much easier. You may thread up to 4 strands of
twine through one straw, but all polyhedra, or even more complex nets, can be
assembled by threading twine at most twice through the same straw. And most of the
time you have to thread twice, in order for your construction to hold its shape well.
Displaying polyhedra: Stretch a string across the ceiling of the room. The straw polyhedra
are so light that many of them can be hung from one string. Be sure that congruent
polyhedra are not hung in the same position, with one string attached to one vertex. Hang
some by attaching 2 strings to the ends of an edge or 3 strings to 3 corners of the same
face, and so on. Planning the use of colors carefully not only adds to their attractiveness,
but also makes assembly easier, and it is important when polyhedra are used as teaching
aids.
Difficulties: Threading is easy, but even small objects, such as tetrahedra, require a long
piece of twine. Every polyhedron (or net) can be fixed together by one long strand of
twine, and we do not know any reasonable design for which we would recommend more
than 3 strands. But a long strand of twine gets twisted and tangled. So you have to
constantly remember to untangle the "needle end" of the twine before threading it through
the next straw. Also tie a small piece of paper or a small light object to the other end of
the twine to prevent it from slipping into a straw. But the main difficulties are conceptual.
Threading the twine to put a polyhedron together can be done in many different ways, but
it is not arbitrary, so planning is important. But even if you make a good plan, what you
see in front of you is a pile of straws, and you have to visualize the object you are
making. This is very difficult for all children and for most adults. In order to overcome this
difficulty, which can make the task impossible, you need teamwork.
Team work: The best team sizes are 2, 3, and 4. With more than 4 people there are too
many hands in the rather small (because of the length of the straws) working space. In
every team only one person holds the needle and untangles the string. The others hold
the straws, keeping enough straws in their correct positions so that visualizing the object
becomes unnecessary. All team members take part in planning what to do next.
Example: 2 students making a tetrahedron. At each moment, 3 straws can lie on the
table, forming a base. One student can hold 2 other straws that are also in their correct
positions. So at no time is more than one edge missing from the final assembly. A very
difficult task becomes easy.
Developing skills: In order to assemble polyhedra with many faces, or other nets
(polyhedra with some edges inside them), students have to build knowledge and skills in
handling many situations, such as, "What to do when 5 edges meet at one vertex? In
what order to thread them?" There are many ways of handling any such situation, but
some are better than others. Learning which methods are better comes from practice and
improved planning, and from evaluating the results.
Making a triangle. (This is a good candidate for the first object to make;
it can be done in kindergarten and 1st grade.)
Task: Make a triangle with 3 straws of different colors, threading it
twice. Leave approximately 1’ of a single strand outside for hanging it for display.
1. Compute the length of twine you need. Measure 1 straw, 8”. Two times passing 3
straws, 2x3x8 = 48”, 4’+ 1’ = 5’ of twine.
2. Cut the twine and thread the needle. Using a ruler, or a yardstick, or a parts of your
body (if you already know their length), measure and cut off 5’ of twine. Gently untangle
it, put a piece of it ½” from the end into the slit in the threading needle, and tie a crumpled
piece of paper with a simple knot 1 - 2” from the other end.
3. Thread the twine. Put 3 straws on the table forming a triangle. Thread the twine
counter clockwise (if you are right-handed), going twice around. Both ends of the thread
Page 51
POLYGONAPALOOZA
will show in 2 straws at the same vertex. Untie the paper and remove the needle. Pull on
both ends of the twine to tighten it. Tie a simple knot connecting the short end and the
long and of the twine. The knot must hold the twine tight.
A second triangle: Make a straw triangle with edges of 3 colors, A, B, C, which will hang
with edge C at the top, and with a vertex pointing down.
A solution: Cut 5’ of twine, and tie a piece of paper 8” from the end. Form a triangle on
your desk, and thread in the following order: A B C A B. Tighten the twine, and tie the
shorter end to the longer end of the string in a location which will make straw C
horizontal.
Straw tetrahedron: If the maximum number of edges that meet at one vertex of a net is k,
and if you want to color the edges so that any 2 edges that meet have different colors,
then you need at least k colors.
There is also a very useful theorem that says that in the situation described above, k+1
colors will always suffice.
When you make a straw polyhedron, making it with colored straws in such a way that in
each vertex, all straws have different colors, is a big help. In such a case, describing how
you thread the straws can be done simply by naming the next color!
A tetrahedron requires 3 colors, for example red R, green G, and blue B. Put 3 straws B,
G, and R on the table, forming the base of your tetrahedron. See how
the other 3 would fit above the base. To distinguish between straws in
the base and straws in the air of the same color, we denoted straws in
the base by "r", "g", and "b" and straws in the air by "R", "G", and "B".
Start at the top, in the air. Thread through, R g r G R b r B G b g B and
tie the ends. (There are many other ways to thread.) Make another
tetrahedron using 4 colors and a different threading pattern.
Straw octahedron: Draw an octahedron. Decide how
to color its edges. It can be done with only 4 colors,
but you may use 5 colors. Plan the threading and
thread. (When you move across a thread, make only
a simple loop around the first one.)
Design another octahedron consisting of 3 squares.
Each square should be a different color! So this time your octahedron consists of only 3
colors.
Planning straw polyhedra: When you draw polyhedra you use some projection. If you
make the polyhedra from poster board, you draw a plan that includes drawing all their
faces to be cut out. When you make a straw polyhedron, you may put straws on a table
to form a pattern that shows what is connected to what. This helps very much as you plan
your color pattern, and it helps you
avoid mistakes in threading.
A pattern for a tetrahedron:
o-o ?
\/\/
o--o
Here, the lines represent straws, the o's represent vertices where the straws join, and a ?
shows that this straw has to join another vertex (in this case, the top leftmost vertex).
Page 52
POLYGONAPALOOZA
A pattern for an
octahedron: o--o--o-?
\/\/\/
o--o--o---?
Again, the top ?
corresponds to the top leftmost vertex, and the bottom ? corresponds to the bottom
leftmost vertex.
A pattern for an icosahedron: Join the letters together. You can thread this pattern
(loosely along vertical lines) on a table, ending in the lowermost ?,
and then tighten it and finish threading in space. For the last steps
an extra pair of hands (or 2 pairs) are very helpful.
Can you design an icosahedron
using 5 colors of straws, such
that each of 5 colors meets at each
vertex?
Visit suggestions:
Cards containing photos of various constructed shapes can be found at the exhibit.
Try making the following geometric solids using the magnetic rods:
Right Square
Pyramid
Diamond
(Octahedron)
Prism
Easy
Difficult
Bridge
Crown
Complex
Diamond
Sources:
Gellert, W., et. al. The VNR Concise Encyclopedia of Mathematics. New York: Van Nostrand
Reinhold Co., 1975.
“Geodesic Gumdrops.” The Science Explorer. Exploratorium-At-Home Book. The Exploratorium.
© 1998. (6/16/03)
http://www.exploratorium.edu/science_explorer/geo_gumdrops.html
Hart, George W. “Soda Straw Tensegrity Structures.” Virtual Polyhedra, ©1997
http://www.georgehart.com/virtual-polyhedra/straw-tensegrity.html
“Regular Polyhedra or Platonic Solids.” EnchantedLearning.com. ©2000-2003. (6/17/03)
http://www.zoomschool.com/math/geometry/solids/index.shtml
Thomas, Rosemary and Jan K. France. “Newspaper Icosahedron.” ©1999-2003. (6/16/03)
http://franceandassociates.net/p/icos/icosahedron.html
Page 53
PVC PIPES
SOUND
Visitors use large foam pads to strike the open ends of eight PVC
pipes, each cut to a different length.
Text Panel:
“What’s this?”
“I’m hitting the opening of the tube, which vibrates the tube, making music. The
more tube to vibrate, the lower the note.”
“All sound starts as a vibration - either the air or the instrument itself must move.
Those vibrations start the air around you vibrating, and those vibrations go into
your ear.”
“Since the vibrations have to travel further in the longer tubes, the note is lower.”
The BIG Idea: Sound is generated by vibrating objects.
A vibrating object moves forwards and backwards in the air. When the surface
moves forward into the air, the molecules of air directly in front of the surface are
compressed (condensation). When the surface moves inward, the molecules of air
directly in front of the surface spread apart, creating an area of low air pressure
(rarefaction). Each condensation and rarefaction make up one sound wave.
The medium through which a sound wave travels does not move. Rather, the
pulse of high and low pressure travels along, transmitted by the individual air
molecules bouncing back and forth into each other.
A forced vibration occurs when an object vibrates as the result of its proximity to
another vibrating object. The natural frequency of an object is one at which the
least amount of energy is needed to produce forced vibrations. Most objects have
one or more natural frequencies. When the edge of an open pipe is hit, the air
column already standing in the pipe vibrates at its natural frequency.
The pitch of the note that results from hitting an open pipe depends on the length
of the air column in the pipe (and therefore on the length of the pipe). Short pipes
have high vibration frequencies that result in high notes. Long pipes have low
vibration frequencies that result in low notes.
Page 54
PVC PIPES
SOUND
Try this at school:
Whelmer #11: Straw Oboes
(Source: Jacobs, Steven. “Straw Oboes.” Whelmers. McREL Accessible Science Series, 1997.)
Description: Reed-like instruments are created from plastic drinking
straws.
Materials
• Plastic or paper drinking straws (paper straws work best)
• Scissors
• Overhead projector (optional)
Instructions
This activity takes some practice to master. You should become proficient at playing a
straw oboe before presenting this activity to your students.
• Flatten one end (about 2 cm) of a drinking straw. Use your teeth or pinch it between
your fingers. Use scissors to make angular cuts as shown, on each side of the
flattened end.
• Insert the straw into your mouth. Position the reed flaps just inside your lips and apply
very light pressure with your lips. Blow through the straw. The reeds should vibrate and
produce a tone. You may need to move the straw around slightly to locate the best
position for creating your musical note. You can cut portions off the non-flattened end
of the straw to create different pitched tones.
Presentation
• If you use this as a class activity, you can demonstrate each step of the fabrication
process with an overhead projector. Place an example of each of the three stages on
the projector surface: regular straw, flattened end, and trimmed reeds.
• Ask students to explain how the sound is being produced. (vibrating reeds cause
surrounding air to vibrate)
• You can play a “do-re-me” scale by cutting 1-cm sections off the end of the straw as
you are blowing through it. Be careful. Do not cut your nose with the scissors.
• You should ask students where they have seen or experienced similar phenomena.
(musical instruments, wind blowing through wires and windows, etc.)
Content
• Blowing through the reeds causes them to vibrate. It also causes the column of air in
the straw to vibrate, producing the pitch characteristic to that length. Cutting the straw
shortens the length of the vibrating column of air, creating a shorter wavelength and
higher frequency (pitch) vibration.
• High-pitched sounds characteristically have shorter wavelengths. Their frequency of
vibration is higher. Frequency is measured in cycles per second or hertz. 5 hertz = 5
cycles per second. 5 kilohertz (5 kHz) = 5000 cycles per second. Low-pitched sounds
have longer wavelengths and lower frequencies.
• Piano tuners will tune the middle A to 440, meaning 440 hertz. The range for normal
human hearing is from 15 cycles per second on the low end of the scale to 15,000
cycles per second at the high end. The reeds of most straw oboes vibrate between 200
and 600 cycles second.
Extensions:
• Allow groups of students to experiment with the straws to make different tones. Have
the reeds and mouthpieces of several reed instruments available along with tubes of
varying lengths and tape. Students can use this equipment and/or the straws to make
Page 55
PVC PIPES
•
SOUND
instruments. They should end with instruments that can produce sounds that they have
predetermined they need to play a familiar song or piece of music.
Students in middle school or above can be challenged to cut the straw to produce a
scale. They should measure and record the straw length for each note. Have them
identify two lengths of straw that produce an octave. They can match the pitch of the
lower straw note to that of a piano note and measure the length of the corresponding
piano string. Have them predict the length of the piano string that will match the pitch
of their higher straw note and report orally or in writing on their discovery.
Visit suggestions:
Have your students experiment with PVC Pipes, paying attention to the following:
•
•
•
•
Does the amount of force used to hit the pipes affect the sound? Does tapping a pipe
lightly with the foam yield a different sound than whacking the pipe with the foam?
Try hitting a pipe so that the foam covers the entire opening vs. hitting the pipe so
that the foam makes contact with the opening’s edge only. Are the sounds that result
the same or different?
Does a pipe yield the same sound if it is hit with the foam on the lower opening, as
opposed to the upper opening?
Do the eight tones form a scale? What would you need to do in order to “tune” the
pipes?
Sources:
Page 56
REBOUND
MOMENTUM
peg
O-ring
Line
Starting
Visitors position large rubber O-rings around pegs
protruding from a slightly sloping, walled
table. Three ball-sized holes are
drilled in the table along its midline.
Visitors release a pool ball from a
starting block at the table’s high end
and watch as the ball bounces around
on its way to the opposite end.
hole
ball
Text Panel:
“By moving the bands to different pegs, I can change the path the ball takes down
the table top.”
“Each change affects the angle and the momentum of the ball.”
“Try it! How many times can you get the ball to bounce before it drops in the
hole?”
“Are the holes targets or traps? You decide!”
The BIG Idea: The outcome of a collision between objects depends on the
material properties of the colliding objects.
The pool ball encounters various objects as it rolls down the table including the
table rim and the O-rings. In each case, the material properties of the object with
which the ball collides effects the outcome of the collision.
The angle of incidence is equal to the angle of
reflection.
At the point on the rim where the ball makes
contact, a tangent to the rim is drawn. The normal
is the line perpendicular to this tangent line,
beginning at the point of ball contact. Both the
angle of incidence and the angle of reflection are
measured from the normal.
Page 57
angle of
incidence
tangent to
table rim at
point of
ball
contact
normal
Pool ball vs. table rim:
In this case, the collision is elastic. This means that both the momentum and total
kinetic energy in the system are conserved. When the pool ball bounces off of the
table rim, the law of reflection is upheld. This law states that:
angle of
reflection
REBOUND
MOMENTUM
Pool ball vs. O-ring:
In this case, the collision is inelastic. This means that while the momentum in the
system is conserved, the total kinetic energy is not. When the pool ball collides
with the O-ring, the O-ring stretches. In order to change shape, the O-ring’s
molecules rearrange, and the internal friction heats the O-ring. Therefore, in this
case kinetic energy is dissipated from the (ball and O-ring) system as heat. When
the ball bounces away from the O-ring, it does not leave with exactly as much
kinetic energy as it had before the collision.
Try this at school:
Intuitive Angles
(Source: Hartshorn, Robert L., et al. “Light.” Physical Science Activities Manual. Center of
Excellence for Science and Mathematics Education at The University of Tennessee at Martin,
Martin, TN, 1994.)
Materials
• Table
• Piece of wood (5 cm x 10 cm x 100 cm)
• Rubber ball
• Pencil / pen / marker
Procedure
• Find a volunteer who claims to be a good pool player for this demo.
• On top of a lab table arrange the piece of wood so that the wide face is perpendicular
to the tabletop.
• In the middle of the board make a mark.
• Place rubber ball approximately 100 cm from the mark and 65 cm from the board
(Position B).
• Challenge the "pool player" to roll another rubber ball in such a manner that it first hits
the mark on the wood (Position A) and subsequently bounces off and hits the first
rubber ball.
• What positional relationship is operating in this effort? Refer to the drawing below.
Angle of Incidence and Angle of Reflection
A
X
Y
·
• The line AD is referred to as the Normal line.
It is perpendicular to the line XY.
• Very likely the "pool player" will be able to
articulate that angle BAD must equal angle
B
D
C
CAD for a ball thrown from C to hit a ball
resting at B.
• We want to call angle CAD the ANGLE OF INCIDENCE; in other words the angle
initially made with the wall and the NORMAL. We want to call angle BAD the ANGLE
OF REFLECTION, or the angle made with the NORMAL when the ball reflected off the
wall.
• As the "pool player" intuitively knew, THE ANGLE OF INCIDENCE EQUALS THE
ANGLE OF REFLECTION.
Page 58
REBOUND
MOMENTUM
Visit suggestions:
Bring these materials with you: paper, pencils, stopwatch, Polaroid camera / film (if
available).
Have small groups of students exercise their problem solving skills using the Rebound
exhibit.
Procedure
Example
•
What is the objective? Before
•
The ball must fall into the 2nd hole on
attempting any experimentation, the
the table.
students should decide on a goal.
•
What are the initial conditions?
•
The ball may be released from any
starting gate.
•
What are the constraints? Students
•
No one may touch the ball once it is
should then decide on a set of
released from the gate.
restrictions.
•
Only 4 O-rings may be used.
•
What is already known?
•
The ball will roll toward the lower end
of the table after it is released.
•
The ball will reflect off of the table
edges.
•
The ball will bounce off of the O-rings.
•
How is success defined?
•
The ball will be released from each
starting gate twice, and each time it will
finish in the 2nd table hole.
•
Find a solution.
•
Try it.
•
Record the results.
•
Once the goal has been successfully
met, draw a diagram of the table and
O-ring positions (or take a picture).
•
Need more of a challenge? Add a
•
The time between the ball’s release
time constraint.
and its entry into the hole must be as
short (or as long) as possible.
•
Repeat the above procedure. Use a
•
Try it.
stopwatch to measure the ball’s travel
time and record the results.
•
Compare results.
•
Get together with other groups and
compare fastest times (and
corresponding path set-ups). Did
everyone come up with the same
solution, or were there multiple ways to
solve the problem?
Sources:
“The Physics of Pool.” Archives: Physics of Sports. Syncopated Science.
http://www.planetutica.org/html/syncopated_science_archived_te.html#Physics%20of%20Billiard
s%20Report
“Re: How come a rubber band becomes hot when you stretch it?” The MAD Scientist Network.
©1995-2000.
http://madsci.wustl.edu/posts/archives/mar99/922225151.Ph.r.html
Page 59
RIVERSCAPE
WATER
Visitors explore methods of manipulating flowing
water in this large metal V-shaped water table. A
Torricelli Tank and a Hero’s Engine (see
descriptions under Background Information) allow
visitors to experiment with water pressure, while
pieces of clear plastic tubing may be used to create
complex waterways.
The BIG Idea: When a liquid is placed in a
container, it exerts pressure against the container’s
walls. This pressure varies with the depth of the liquid. The more liquid in the
container, the greater the pressure at the bottom of the container.
Torricelli Tank
•
A liquid in a container exerts a force against the insides of the container and
against any object submerged in the liquid. The exerted force divided by the
area of the parts of the container on which it acts is defined to be the pressure
exerted by the liquid.
Pressure = force /area
•
At any point within the liquid, the forces that produce
pressure are exerted equally in all directions.
•
The force exerted by the liquid on the bottom of the
container is equivalent to the weight of the liquid in the
container.
•
The weight of a liquid depends on its weight density,
water level
where
window
weight of liquid
weight density =
volume of liquid
Torricelli Tank
So, the pressure exerted by the liquid can be rewritten as:
pressure =
weight (weight density x volume)
=
area
area
Because the volume of a container = area x depth,
(weight density x area x depth)
= weight density x depth
area
Thus, the pressure that a liquid exerts on the insides of a container depends only
on its density and the depth of the container.
•
We assume that the density of the liquid is constant with respect to the depth
of the liquid. Therefore, at any given depth, a given liquid exerts the same
pressure on any surface.
•
When the liquid is pressing against a surface, there is a net force directed
perpendicular to the surface. If there is a hole in the surface, the liquid initially
moves perpendicular to the surface. It is then effected by gravity, which curves
the path of the escaping liquid downward.
pressure =
Page 60
RIVERSCAPE
•
WATER
The deeper the water, the greater the net force against the surface, the greater
the horizontal velocity of the liquid. (The farther it gets from the container
before gravity can pull it downward.)
Hero’s Engine
•
Hero, an engineer in ancient Greece, is thought to
have built the first steam engine*. Jets of steam
spouted out of the engine, causing it to spin in a circle.
The Hero’s Engine found in the RiverScape exhibit
component, is similar in that water spouts out of two
jets, turning the entire device.
•
As is described under “Torricelli Tank”, the water
pressure at any level in the container depends on its
depth (defined from the water’s surface vertically to the
water level in question). Therefore, the pressure at the
outlet valves increases as the engine tank is filled.
Increasing the amount of water in the tank results in a
faster spinning engine.
water
water
Hero’s Engine
In summary, the more water in the tank, the higher the water pressure at the
valve openings, the greater the horizontal velocity of the escaping water, the
faster the engine turns.
* For a translation from the original Greek of “The Pneumatics of Hero of Alexandria”, check out
this website: http://www.history.rochester.edu/steam/hero
Try this at school:
Soda Pop Can Hero Engine
(Source: Clausen, Tom, and Roger Strom, ed. “Soda Pop Can Hero Engine.” NASA Teacher’s
Resource Center. Aerospace Education Services Project, Oklahoma State University. (8/04/2000)
http://www.grc.nasa.gov/WWW/K-12/TRC/Rockets/hero.html)
Description: Water streaming through holes in the bottom of a suspended soda pop can
causes the can to rotate.
Materials
• Empty soda pop can with the opener lever intact
• Nail or ice pick
• Fishing line
• Bucket or tub of water
Procedure
• Lay the pop can on its side and using the nail or ice pick carefully punch four equally
spaced small holes just above and around the bottom rim. Then before removing the
punching tool for each hole, push the tool to the right (parallel to the rim) so that the
hole is slanted in that direction.
• Bend the can's opener lever straight up and tie a short length of fishing line to it.
• Immerse the can in water until it is filled. Pull the can out by the fishing line. Water
streams will start the can spinning.
• If the can does not spin try making the holes larger or adding a fishing swivel to the
string above the can.
Page 61
RIVERSCAPE
WATER
Visit suggestions:
Bring these materials with you: graph paper, pencils, plastic rulers, tape measure.
Experiment with the Torricelli tank:
•
Have your students set up tables to record the
following information, where:
D
(cm)
h = D-d
(cm)
D is the water depth, from the surface of the water
in the tank to the tank’s base.
d is the vertical distance from the base of the tank to the
center of the lowest hole in the tank wall.
h is the height of the water in the tank above the hole,
D
measured from the center of the lowest hole.
X is the horizontal distance between the tank wall (at the point
where the water exits the hole) and the point where the arc of
water meets the table.
•
•
•
h
d
X
Using the plastic tubing found at the RiverScape exhibit, fill the tank.
Set up two rulers, as shown, to measure distances D and X.
As the water drains out of the tank, measure and record distance X when the water
depth, D, reaches predetermined points. (For instance, record X as D decreases by 2cm intervals.)
Subtract the distance, d, from the depths D to find the heights, h, of the water in the
tank above the hole at each interval.
Graph X vs. h.
What conclusions can be drawn from the results?
X (cm)
•
•
•
X
(cm)
h (cm)
Sources:
“ Evangelista Torricelli.” Fluid Mechanics Hall of Fame. (8/07/2000).
http://mech.postech.ac.kr/fluidmech/history/Torricelli.html
(Note: This site no longer exists. 6/03)
Page 62
ROBOTIX® TABLE
Visitors use Robotix® motors, wheels, axles, and
connectors to create machines that move when plugged in
to the table’s power supplies.
Text Panel:
“…oh, the axle’s connected to the camshaft....”
“What are you making?”
“I’m making some machines with these Robotix® pieces. Combining motors,
wheels and body pieces makes rovers, space ships...”
“...even motorized spiders - anything I can design!”
“What can you make?”
The BIG Idea: Motors convert electrical energy into mechanical energy.
Robotix® motors allow visitors to create machines that actually work. The motors
are housed in black boxes with two connecting pins on one end.
One end of a wire (found on the
table) is plugged into the motor
while the other end is plugged in
below a red button on the power
supply box.
The motor is activated when
the upper section of the
red button is pushed.
Activating the
motor causes its
external shaft to rotate.
wire
connecting
pins
external shaft
wire
Robotix® Motor External
magnets
motor
gears
wire
connecting
wire coils
pins
Robotix® Motor Internal
Anything connected to the rotating external shaft will spin when the motor is on.
To change the direction of the rotation, either
1) press the lower section of the red button,
or 2) plug the wire into the power supply such that the pins are
reversed.
Page 63
ROBOTIX® TABLE
Because the Robotix® motors’ working parts are not visible from the outside, Try
this at school:
Beakman's Electric Motor
(Source: Palmer, Christopher M.
(9/22/2000))
http://fly.hiwaay.net/~palmer/motor.html
“Beakman’s Electric Motor, as seen in Beakman’s World.
Materials
• One 'D' Cell Alkaline Battery
• One Wide Rubber Band
• Two Large Paper Clips
• One Rectangular Ceramic Magnet
• Heavy Gauge Magnet Wire (the kind
with red enamel insulation, not plastic
coated)
• One Toilet Paper Tube
• Fine Sandpaper
• Optional: Glue, Small Block of Wood for Base
Procedure
• Starting about 3” from the end of the wire, wrap the wire 7 times around the toilet
paper tube. Remove the tube (you don't need it any more). Cut the wire, leaving a 3inch tail opposite
the original starting point. Wrap
the two tails around the coil so
that the coil is held together and
the two tails extend
perpendicular to the coil.
See illustration at left.
Note: Be sure to center the two
tails on either side of the coil.
Balance is important. You might
need to put a drop of glue where
the tail meets the coil to prevent
slipping.
•
On one tail, use fine sandpaper to completely remove the insulation from the wire.
Leave about 1/4" of insulation on the end and where the wire meets to coil. On the
other tail, lay the coil down flat and
lightly sand off the insulation from
the top half of the wire only. Again,
leave 1/4" of full insulation on the
end and where the wire meets the
coil.
•
Bend the two paper clips into the
following shape (needle-nosed pliers may be useful)
•
Use the rubber band to hold the
loop ends (on the left in the paper
clip drawing) to the terminals of
the "D" Cell battery:
Page 64
ROBOTIX® TABLE
•
Stick the ceramic magnet on the side
of the battery as shown:
•
Place the coil in the cradle formed
by the right ends of the paper clips.
You may have to give it a gentle
push to get it started, but it should
begin to spin rapidly. If it doesn’t spin,
check to make sure that all of the
insulation has been removed from the wire ends.
If it spins erratically, make sure that the tails on the coil are centered on the sides of
the coil. Note that the motor is "in phase" only when it is held horizontally (as shown
in the drawing).
•
For display, you will probably need to
build a small cradle to hold the motor
in the proper position. It might also help
to bend the ends of the coil a bit so that
as it slips right or left, the bends keep it in the proper position.
Here is a diagram of the finished motor:
Visit suggestions:
Build a Vehicle
To build a vehicle with wheels,
connect one wheel to the motor such that the
rotating shaft connects to the fixed wheel axle
(connecting the free axle to the rotating shaft
results in a tire sitting still on the table).
Connect the free axle of another wheel to a fixed
connector point on the motor. Connect the motor
to the power supply, push the corresponding button,
and your vehicle should slowly move across the table.
wheel
free axle
(RED) fixed axle
Sources:
Company, 1986.
“Magnets and Motors” Student Activity Book, National Science Resources Center / Science and
Technology for Children. Smithsonian Institution - National Academy of Sciences, 1991.
Page 65
ROLLER RAMPS
MECHANICS
Visitors create a roller coaster track on a table using a series of repositionable
ramp, hill, and flat sections.
Visitors then place one of two wheels at the beginning of the track. Although the
wheels have equal mass, one wheel’s mass is concentrated at its rim while the
other’s is concentrated about its axle.
rim
axle
Wheel 2: Mass
concentrated about axle
Wheel 1: Mass
concentrated at wheel rim
A timer on the table may be used to measure the time needed for each wheel to
complete the coaster course.
Text Panel:
“Finally! A roller coaster I won’t get sick on!”
“Rearrange these sections, then experiment with the wheels.”
“Both wheels have the same weight, but it is in different places on each wheel.
This affects the rotational inertia - how hard it is to get something to start
spinning.”
“What’s the difference?”
“A figure skater knows this answer - they pull their arms in to spin faster, and
spread them out to slow down.”
The BIG Idea: The rate at which a spinning object rotates about an axis depends
not only on its mass, but also on the distribution of that mass.
Inertia is the property of matter that has to do with resistance to change. As
Newton’s first law of motion states: a body at rest tends to remain at rest while a
Page 66
ROLLER RAMPS
MECHANICS
body in motion tends to remain in motion. The more inertia an object has, the
more difficult it is to alter the object’s state of rest or motion (to get it to move,
stop, slow down or speed up).
Rotational inertia has to do with an object's resistance to changes in its rotational
state of motion. The more rotational inertia an object has, the more difficult it
becomes to make it spin (if it is at rest) or to make it change its rate of spin (if it is
already spinning).
Rotational inertia, I, is a quantity that can be calculated.
For a hoop with mass, m, concentrated at the rim, rotating
at a distance, r, about an axis, the rotational inertia,
mass, m
I = mr2.
The further the mass is concentrated from the rotational
axis, the larger the rotational inertia. The more rotational
inertia, the more difficult it is to rotate the object.
r
•
Because the two wheels used in this activity have the same mass, we can
approximate them as shown.
•
All of Wheel
1’s mass is
assumed to be
concentrated at
the rim, while
all of Wheel 2’s
mass is
assumed to be
concentrated
about its axle.
APPROXIMATE:
r1
AS:
Wheel 1
Wheel 1
APPROXIMATE:
r1
r2
AS:
r2
•
Because r1,
Wheel 2
Wheel 2
the radius of
Wheel 1 is
larger than r2, the radius of Wheel 2, the rotational inertia of Wheel 1 is greater
than that of Wheel 2. Thus, we expect that when beginning from rest, Wheel 1
will have to overcome more inertia than will Wheel 2 to begin rolling down the
track.
•
At the top of the track both Wheel 1 and Wheel 2 will have the same potential
energy, PE = mgh where m is the mass of either wheel (their masses are
equal), g is the acceleration of gravity, and h is the height of the track above the
table.
Page 67
ROLLER RAMPS
•
MECHANICS
At the bottom of the ramp, each wheel will have transformed all of its
potential energy into kinetic energy (both translational and rotational).
PE =KETOTAL = KETRANSLATIONAL+ KEROTATIONAL = ½mv2 + ½ I ω2
where m is the mass of the wheel, v is the linear velocity of the wheel, I is
the moment of inertia of the wheel and ω is the rotational velocity of the
wheel.
•
Overcoming rotational inertia will expend more of Wheel 1’s potential energy
than Wheel 2’s. Therefore, Wheel 1 will have less leftover potential energy to
transform into translational kinetic energy than will Wheel 2. Wheel 1 will
move along the track more slowly than Wheel 2 and so Wheel 2 will win the
race.
Downhill Race
http://www.exploratorium.edu/snacks/downhill_race.html
Description: Two cylinders that look the same may roll
down a hill at different rates. Two objects with the same
shape and the same mass may behave differently
when they roll down a hill. How quickly an object
accelerates depends partly on how its mass is distributed.
A cylinder with a heavy hub accelerates more quickly than
a cylinder with a heavy rim.
materials
• 2 identical round metal cookie tins (such as those from butter cookies).
• 10 large metal washers (about 1/4 pound [112 g] each).
®
• Double-sided foam stick-on tape (or adhesive-backed Velcro ).
• A ramp.
assembly: (15 minutes or less)
• Arrange five of the washers evenly around the outside rim of the bottom of one tin.
• Stack five washers in the middle of the bottom of the second tin.
®
• In both cases, secure the washers with tape or Velcro .
to do and notice: (15 minutes or more)
• Place both tins at the top of the ramp. Be sure the tops are on.
• Ask your friends to predict which tin will reach the bottom of the ramp first.
• Release the tins and let them roll down the ramp.
Note: The tin with the mass closer to the center will always reach the bottom first.
©1997 The Exploratorium, 3601 Lyon Street, San Francisco, CA 94123.
Page 68
ROLLER RAMPS
Momentum Machine
MECHANICS
http://www.exploratorium.edu/snacks/momentum_machine.html
Description: How ice-skaters, divers, and gymnasts get themselves spinning and twisting
faster. You've probably seen an ice skater spinning on the tip of one skate suddenly start
to spin dramatically faster. A diver or gymnast may also suddenly flip or twist much faster.
This speeded-up rotation results from a sudden redistribution of mass. You can make
yourself suddenly spin faster while sitting in a rotating chair.
materials
• A rotating stool or chair from a scientific supply house, an office supply store, or a
classroom.
• 2 heavy masses. Use the heaviest weights that you can support at arm's length.
• A partner.
• Adult help.
to do and notice
• Sit in a chair with one of the masses in each hand and with arms outstretched.
• Have your partner start rotating you slowly, then have that person let go and move
away.
• Quickly pull the masses inward and notice that you rotate faster. Be careful! A very
rapid spin may cause the chair to tip over! Also, you may be dizzy when you get up.
what’s going on?
A rotating object tends to remain rotating with a constant angular momentum unless it is
acted upon by an outside twisting force. The definition of angular momentum is slightly
more complex than that of linear momentum. Angular momentum is the product of two
quantities known as angular velocity and moment of inertia. Angular velocity is merely
velocity measured in degrees, or radians-per-second, rather than meters-per-second.
A person sitting on a rotating chair or stool approximates a system in which angular
momentum is conserved. The friction of the bearings on the chair stem serves as an
outside twisting force, but this force is usually fairly low for such chairs. Since angular
momentum is conserved, the product of angular velocity and moment of inertia must
remain constant. This means that if one of these factors is increased, the other must
decrease, and vice versa. If you're initially rotating with your arms outstretched, then
when you draw your arms inward, your moment of inertia decreases. This means that
your angular velocity must increase, and you spin faster.
etcetera
The conservation of angular momentum explains why an ice skater starts to spin faster
when he suddenly draws his arms inward, or why a diver or gymnast who decreases her
moment of inertia by going into the "tuck" position starts to flip or twist at a faster rate.
Page 69
ROLLER RAMPS
MECHANICS
Visit suggestions:
Bring these materials with you: paper, pencils.
Have small groups of students try the following:
Procedure:
Construct a track using the ramp, hill, and flat sections available. Draw your track here:
Draw each wheel below. Make sure to show the differences between the two wheels.
Wheel 1
Wheel 2
What are the differences between Wheel 1 and Wheel 2?
Place Wheel 1 at the beginning of the track. Using the table’s built-in timer, measure
how long it takes for the wheel to reach the track’s end (finish time). Record and repeat
for a total of three trials. Repeat using Wheel 2
Wheel 1
Wheel 2
Trial 1, finish time
Average finish time
Which wheel won the race? Looking over the information that you have recorded, why
do you think it won?
Sources:
“Downhill Race.” Exploratorium Snacks. The Exploratorium, 3601 Lyon Street, San Francisco,
CA 94123.
http://www.exploratorium.edu/snacks
“Momentum Machine.” Exploratorium Snacks. The Exploratorium, 3601 Lyon Street, San
Francisco, CA 94123.
Weast, Robert C., Editor-in-Chief. CRC Handbook of Chemistry and Physics. 66th ed., Boca
Raton, FL: CRC Press, Inc., 1986.
Page 70
SOUND DELAY TUBE
SOUND
Visitors hold the funnel-covered end of a 250-foot tube to one ear
and hear themselves talk while speaking into the tube’s other
end.
Text Panel:
“Try saying a rhyme into this 250-foot tube while listening at the other end.”
“Sound waves travel through the air at a speed of about 1,100 feet per second. At
this speed, sounds traveling a short distance are heard almost immediately. When
sound travels a greater distance, you can hear the delay.”
“You can use the speed of sound to measure distance. It takes about 5 seconds
for sound to travel 1 mile. So if it takes 10 seconds to hear thunder after seeing
lightning, a storm is about 2 miles away!”
“Try it!”
The BIG Idea: Sound travels at a finite speed.
The Speed of Sound: The speed of sound varies with the medium through which
the sound travels. In the air, the speed of sound varies with temperature and
humidity. However, these variations are fairly slight:
For example, the speed of sound in air at 0°C = 331 m/s = 1086 ft/s =.21 miles/s,
but at 20°C = 343 m/s = 1126 ft/s =.21 miles/s.
In general, it takes approximately 5 seconds for sound to travel 1 mile.
Note that the warmer the traveled-through medium, the faster the sound travels.
The molecules in a warm medium are already moving more quickly than they
would in a cold medium. Thus, they transmit pulses through the medium more
quickly than do cold, slower-moving molecules.
The Sound Delay Tube is 250 feet long. This means that it should take:
1 second
250 feet x
= .22 seconds
1126 feet
for the sound of your voice going in one end of the tube to come out the other.
While .22 seconds does not seem like a long period of time, it is noticeable when
you are listening to yourself talk into the tube.
The Speed of Light:
Sound moves much more slowly than does light. The speed of light in a vacuum
= 3.0 x 108 m/s, = 9.8 x 108 ft/s, = 1.86 x 105 miles/s. This means that it takes
Page 71
SOUND DELAY TUBE
SOUND
light approximately 5.4 x 10-6 (0.0000054) seconds to travel 1 mile; much faster
than sound can travel!
Try this at school:
Speed of Sound
http://www.lessonplanspage.com/ScienceSpeedSound8.htm
(Source: Kuntzleman, Tom. “Speed of Sound.” Lesson Plans Page. (9/13/2000).)
Grade Level: 8
Materials
• Tuning forks
• Graduated cylinders
• Water
• Rulers with centimeter markings.
Introduction
Sound is a wave. The speed of any wave can be found with the equation:
speed = frequency x wavelength
The wavelength of a sound wave can be found by allowing the sound wave to pass near
a tube. When the length of the tube is one-quarter the wavelength, the sound wave will
resonate. This means that the sound wave will get stronger (louder). By finding the length
of a tube that causes a sound wave to resonate, the wavelength of the sound wave can
be calculated. If the frequency of the tuning fork is known, the equation above can be
used to find the speed of the sound wave.
Procedure:
1. Put some water into a 100mL or 500mL graduated cylinder.
2. Tap a tuning fork on a soft object and place the fork near the opening of the graduated
cylinder.
3. If the sound resonates (gets loud), proceed to step 5.
4. If the sound does not resonate, either add or remove water then to back to step 2.
5. Measure the distance in centimeters from the top of the water level to the top of the
graduated cylinder. Record this distance.
6. Convert the distance in step 5 to meters.
7. Multiply the distance recorded in step 6 by 4. This will give you the wavelength of the
sound wave.
8. Now look at the tuning fork you used. There should be a number printed on the tuning
fork. This number is the frequency of the sound wave.
9. Using speed = frequency x wavelength, calculate the speed of the sound wave.
10. Your answer will be in units of meters/second.
11. Repeat the experiment using different frequency tuning forks. You should get the
same speed for different tuning forks.
Note: Most students usually find the speed of sound in this experiment to be around 345 m/s.
Visit Suggestions:
Have your students complete the following calculation:
Given that the Sound Delay Tube is 250 ft long and that at room temperature, sound
travels at 1126 ft/s, how long should it take for you to hear your own voice after speaking
into the tube. (Note: calculations shown on previous page.) Try listening / speaking into
the tube. Does your calculated answer seem to be accurate?
Sources:
Page 72
STROBE SCULPTURE
STROBE STATION
LIGHT / OPTICS
Strobe Sculpture
A vibrating metal sculpture is lit by a
variable-frequency strobe light.
Visitors use control panel buttons to
manipulate the strobe frequencies
and then observe the results.
Multi-Chromic 111
(Diffraction)
Wen-Ying Tsai / 1970
From the collection of
Dr. and Mrs. Allen Metzer
Visitors are given the following
FASTER
choices at the Strobe Sculpture
STROBE
exhibit:
PLAY
The FASTER STROBE / SLOWER
MUSIC
STROBE choices allow the visitor
to speed up /slow down the
SLOWER
frequency of the strobe light
STROBE
flashes.
Strobe Sculpture Control Panel
The PLAY MUSIC button
activates recorded music. Loud
sounds activate the strobe flash, so the sculpture appears to move synchronously
with the music.
Text Panel:
“Change the speed of the flashing strobe light pointed at the moving sculptures.”
“Or play the music or use your voice!”
“As the speed of the strobe changes, you see the jiggling sculptures at different
micro-second intervals. This makes their movement appear to move, change or
freeze. But the sculptures never change speed!!”
“This ‘persistence of vision’ is how movies and TV seem to move!”
“Movies flash 24 pictures every second; television uses 30.”
The BIG Idea: Rapidly flashing strobe lights may alter our perceptions of objects
in motion.
Page 73
STROBE SCULPTURE
STROBE STATION
LIGHT / OPTICS
Strobe Station
Visitors place an 8-inch disk containing pictures / designs onto a vertical
turntable. A variable-frequency strobe light is projected onto the spinning disk.
Visitors press buttons on the back of the projector to change the
strobe
light’s frequency.
Flashes Per Second
Replaceable
Disk
Strobe Light
SLOWER
FLASHING
Text Panel:
FASTER
FLASHING
“What’s happening here?”
“I’m changing the speed of the flashing strobe light, not the speed of the disk.”
“As the speed of the strobe changes, you see the picture at different micro-second
intervals. This makes the image appear to move, change or freeze. But the disk
never changes speed!!”
“You can switch the disks just by grabbing them.”
“This ‘persistence of vision’ is how movies and TV seem to move.”
The BIG Idea:
A strobe light can be used to determine the rotational frequency of a spinning
object.
Background Information Strobe Sculpture / Strobe Station:
A strobe light is a lamp that flashes quickly enough to “freeze” the motion of
some moving objects.
At the Strobe Sculpture exhibit, a metal sculpture vibrates at specific frequencies.
These frequencies do not change. The strobe light flashes at frequencies chosen
by the visitor.
Each time the strobe light flashes, the visitor sees the sculpture “frozen” in its
position at that instant (similar to a flash photograph). As a result of the
persistence-of-vision phenomenon, the visitor’s eyes and brain retain these images
long enough to fill in the between-the-flash gaps, connecting them together. To
the visitor, the sculpture does not appear to vibrate (their actual movement), but
rather to move slowly back and forth.
Page 74
STROBE SCULPTURE
STROBE STATION
LIGHT / OPTICS
At the Strobe Station, a disk is placed on a turntable axle that is
moving at a specific frequency. This frequency does not
change. The strobe light that is projected on the disk flashes at a
frequency chosen by the visitor (33-167 flashes / second).
direction
of disk
rotation
With each flash of the strobe light, the visitor sees the image on
the disk at that instant’s orientation. Persistence of vision
allows the visitor to connect the images together, perceiving
continuity between them.
When the frequency of the turntable and the frequency of the strobe are exactly
the same (or are multiples of each other), the strobe flashes once each time the
disk completes one full rotation on the axle. The visitor perceives the images on
the disk to be fixed, because each time the light flashes, the image is oriented in
exactly the same direction. So, although the disk is spinning very rapidly in a
clockwise direction, the visitor sees the following:
and perceives
the disk to be
stationary.
Flash 1
Flash 2
Flash 3
Flash 4
Flash 5
If the strobe is
flashing at a frequency that is higher than that of the spinning disk, the visitor sees
the following:
and perceives
the disk to be
slowly rotating
counterclockwise.
Flash 1
Flash 2
Flash 3
Flash 4
Flash 5
If the strobe is flashing at a frequency that is lower than that of the spinning disk,
the visitor sees the following:
and perceives
the disk to be
slowly rotating
in a clockwise
direction.
Flash 1
Flash 2
Flash 3
Flash 4
Flash 5
Thus, a strobe
light can be used to determine the frequency of a rotating object. When the
moving object appears to be stationary under the strobe light, the frequency of the
object equals the frequency of the strobe flashes. Auto mechanics use a strobe
light to measure the RPM of car engines. This device is called an engine timing
light.
Page 75
STROBE SCULPTURE
STROBE STATION
LIGHT / OPTICS
Persistence of Vision
http://www.exploratorium.edu/snacks/persistence_of_vision.html
Description: Your eye and brain hold on to a series of images to form
a single complete picture. When you look through a
narrow slit, you can see only a thin strip of the world
around you. But if you move the slit around rapidly,
your eye and brain combine these thin strips to make
a single complete picture.
materials
• Cardboard mailing tube approximately 3-inch
diameter and 2-3 ft long, with a cap over one end.
• A sharp knife.
• With a knife, cut a slit in the cap of the mailing tube. The slit should be about 1 inch
(2.5 cm) long and 1/8 inch (3 mm) wide. Replace the cap on the end of the tube.
• Close one eye. Put the other eye to the open end of the tube. Cup your hand around
the tube to make a cushion between the tube and your eye. Hold the tube so that the
slit is vertical.
• When the slit is stationary, you can't see much. Keep your head and body still and
sweep the far end of the tube back and forth slowly while you look through it. Increase
the scanning speed and compare the views. Notice that when you sweep the tube
quickly from side to side, you can obtain a rather clear view of your surroundings.
etcetera
• The Viking 1 and 2 landers photographed the surface of Mars by recording narrow-slit
images that were transmitted to earth and assembled by computer to make the final
surface photographs. As this demonstration shows, your eye and brain can "take a
photograph" in the same way.
Whirling Watcher
http://www.exploratorium.edu/snacks/whirling_watcher.html
Description: A series of slits moving rapidly past your eye allows you to see images in
short bursts. Such rapid but fragmented views of moving
objects can make the objects appear to jerk along,
change speed, or even move backward.
materials
• Copy of the stroboscope disk template provided.
• Posterboard for backing the stroboscope disk.
• Access to a copy machine.
• A large mirror.
• A glue stick or suitable adhesive for mounting the disk to the backing.
• A rotator for the stroboscope disk. You can use a variable-speed electric drill, hand
drill, portable electric mixer, electric screwdriver, or pencil and pushpin.
• Scissors or utility knife.
• Running water
• Black posterboard to use as a background for the water.
• A partner.
®
• Optional: adhesive-backed Velcro
Page 76
STROBE SCULPTURE
STROBE STATION
LIGHT / OPTICS
• Print out the stroboscope pattern provided. Enlarge it if you wish. Cut out the pattern
and glue it to the posterboard.
• Cut the posterboard to the same shape as the stroboscope, including the slits. You
can cut with a good pair of scissors alone, or use scissors in combination with a utility
knife.
®
• Mount the stroboscope disk on the rotator. You can use adhesive Velcro to mount
the disk to the electric drill or other device. If you use a drill with a chuck, you can use a
bolt as a shaft, with two nuts to hold the disk. (You can also make a simple manual
rotator by simply sticking the pushpin through the center of the disk and into the end of
a pencil or wooden dowel.)
• Close one eye. Hold the stroboscope so that the side with the horses is facing away
from you, and so that you can see through a slit with your open eye. Spin the disk and
look through the slits at your surroundings. Notice that you can see the entire scene on
the other side of the disk, not just one small strip of it.
• Try spinning the disk faster, then slower, and compare the results.
• Have a friend hold a hand so that you can see it through the spinning disk. Ask your
friend to move his or her hand from side to side. Notice that the movement you see is
jerky rather than smooth. Have your friend move his or her hand rapidly, and then
slowly. Notice that the amount of jerkiness changes as the speed of the hand
movement changes.
• Stand facing a mirror, and hold the disk and rotator in front of you. Be sure the disk is
mounted on the rotator so that the horses are facing the mirror. Spin the disk and
watch its reflection in the mirror through one of the slits. Concentrate your attention on
one of the horses, and you will see it gallop!
• Let water run slowly enough to produce a stream that breaks up into separate droplets
as it falls. Place a black background behind the well-illuminated drops of water. Look
through the spinning stroboscope and watch the water-droplets fall in slow motion.
Vary the stroboscope's speed and see if you can make the water-droplets stand still or
even look as if they are moving upward.
etcetera
• Place a bicycle upside down and spin a wheel. Look at the spinning spokes through
the slits in the Whirling Watcher. You can see the spokes stop, or move slowly forward
and backward like the wheels on a moving stagecoach in an old Western. In modern
Westerns, special wheels with unevenly spaced spokes are put on the stagecoaches
to avoid the strange appearance of backward rotation when the moving wheels are
filmed. A regular set of wheels with evenly spaced spokes is used for scenes in which
the stagecoach is not moving.
• You can exercise your creativity by making your own moving pictures. On the
opposite side of the Whirling Watcher disk from the horses, in the space between each
pair of slots, draw images, each slightly different from its neighbors. (A running stick
figure is an easy set of images to start with.) Look through one of the slots at a mirror,
just as you did with the horses, and spin the disk.
For more information about devices like this (called zoetropes, fantascopes, or phenakistoscopes),
see the book Seeing the Light, by David Falk, Dieter Brill, and David Stork (Harper & Row, 1986, p.
195).
Page 77
STROBE SCULPTURE
STROBE STATION
LIGHT / OPTICS
Stroboscope Disk Template:
Visit suggestions: Strobe Station
Have your students determine the frequency of the rotor’s spin.
•
•
•
•
•
Place a disk on the rotor.
Change the strobe light’s frequency until the disk’s picture appears stationary.
Record the frequency of the strobe light.
Repeat for several disks.
Are the recorded frequencies the same each time? Why or why not?
Sources:
“Stroboscope.” Funk and Wagnalls Knowledge Center. 2000.
http://www.fwkc.com/encyclopedia/low/articles/s/s024001247f.html
(Note: This site no longer exists. 6/03)
“Re: What is a stroboscope and how does it work?” The MAD Scientist Network. ©1995-2000.
http://madsci.wustl.edu/posts/archives/dec97/877386465.Ph.r.html
“Use Flashers.” Exhibit text. Square Wheels…Driving Science Home. Ohio’s Center of Science
and Industry, 1994.
Page 78
STRUCTURES STATION
MECHANICS
Visitors have the opportunity to build structures using different sizes and types of
construction materials. Small blocks may be used to create model structures on a
table, while larger blocks may be used to build structures on the floor. Different
types of construction sets are rotated through the exhibit every four months.
Text Panel:
“I’m building a skyscraper!”
“What can you learn about a structure by looking at its shape?”
“Depending on the ground, the materials, the purpose and even the culture, each
building or bridge will be designed and built differently!”
“What kind of structures can you design?!”
The BIG Idea: For a building to remain standing, its center of mass must be
located above its supporting base. Assuming this to be the case, the lower the
center of mass, the more stable the structure.
An object’s center of mass is the point of average mass distribution for the object.
An object’s center of gravity is the point located at the center of the object’s
weight distribution.
•
For any everyday object located on the earth, the center of mass and center of
gravity are the same. (This would not be the case in outer space or if an object
was large enough for the its gravitational distribution to vary.)
center of mass
•
When the object’s shape is
of an equilateral
symmetrical and it is constructed
from a single type of material,
triangle
the center of mass is at its
center of mass
geometrical center. If the
of a cube
object is not symmetrical and/or
is made from a number of materials, the center of mass is more difficult to
determine.
An object’s stability depends on two criteria: 1) the area of the base of the object
and 2) the height of its center of mass.
•
When moving an object in any direction raises its center of mass, it is said to
be in a state of stable equilibrium.
•
An object will fall over if its center of mass is not located above its supporting
base. This is called a state of non-equilibrium. If its center of mass is located
above its supporting area, it is considered to be in a stable state and will remain
upright.
Page 79
STRUCTURES STATION
MECHANICS
a
Å The block at the left is in stable equilibrium.
The center of mass • is located above the
c supporting base (side bc). If the block is tipped,
b
its center of mass will be raised from its
original position. (See next diagram).
a
Å Even though it has been tilted onto corner b,
the block’s center of mass is still located above
c bc, and so when it is free to do so, the block
b
will return to its position of stable equilibrium,
as seen above.
Å The block is now in a state of nonequilibrium and will topple over. The center of
a
mass is no longer located above side bc.
c
Instead it is located over side ab. Thus, the
block will come to rest on side ab (as seen
b
below).
Å The block is again in a state of stable
c
equilibrium. The center of mass is located over
side ab (the block’s supporting base). The
b
a
block is more stable than it was initially.
Unbalancing the block now would require
tilting it such that the center of mass would no longer be located above side ab.
This would require more effort than it would to move the block to an unstable
position when it was standing on side bc.
When constructing a building, the wider the base and lower the center of mass of
a building, the less likely it is to topple over.
Try this at school:
Sumos & the Center of Mass
http://www.nsta.org/main/news/stories/journal_archive_date_list.php?category_ID=87&issue_ID=6
87 (Note: To access article on this site, user must be an NSTA member. 6/03)
(Source: Vasquez, Vanessa A. “Sumos and the Center of Mass.” Science Scope. March 1999: 1114.)
It is true that science can be found anywhere, even in the ancient Japanese sport of
sumo wrestling. The object of the sport is to push your opponent, (who often weighs over
400 pounds) out of the dohyo (wrestling ring) using grace, skill and clever techniques.
"So," you are probably asking yourself, "what does sumo wrestling have to do with
science?" Well, sumo wrestling techniques rely heavily on physics, specifically the
concept of center of mass. You can begin this lesson by reading a traditional Japanese
folk story such as Peach Boy. After reading the story, draw a Venn diagram on the
chalkboard to compare and contrast Japanese and American cultures. If sumo wrestling
comes up, compare and contrast it with the style practiced by your school’s wrestling
team. At the end of the discussion it is time to introduce your special guest - an amateur
sumo wrestler, (if you do not have a sumo association in your area, ask a wrestler in the
heavy weight division on your local high school team to visit your classroom). Students
will be fascinated by your guest and will have lots of questions. "Why are sumo wrestlers
so big?" is a great question because it leads right into the lesson on the center of mass.
Page 80
STRUCTURES STATION
MECHANICS
Sumo wrestlers are large because having a big stomach lowers their center of mass.
This gives them better balance and makes them more difficult to push around the ring.
To demonstrate this, ask our guest wrestler to stand directly in front of you at less than an
arm’s length. Next have him push one of your shoulders. You will most likely move and
lose your balance. Once you’ve recovered, ask him to push you again, but this time
spread your feet apart and crouch down. Were the results the same? Ask your students
to explain why it was harder to move you the second time. This demonstration definitely
captures students’ interest because it is not every day that they see their teacher being
pushed by a sumo wrestler.
Explain to students that the center of mass is an imaginary point where, for convenience
in certain calculations, the total weight of the body may be thought to be concentrated. In
order to tip the body over, its center of mass must be tilted beyond the point of rotation. In
the case of the sumo wrestler, his center of mass just below his belly must be tipped past
outside the edge of his foot. Therefore, by lowering his center of mass and spreading his
base he makes it more difficult for his opponent to tip him over.
Follow up this discussion with a hands-on demonstration of what happens when you
lower the center of mass below the point of rotation. For this demonstration, each group
of students will need a small potato, two forks, a sharpened pencil and an empty water
glass. Have each group carefully insert the pencil into the center of their potato.
Then charge the groups with the task of balancing the potatoes on the pencil erasers
atop the inverted water glasses. After a few frustrating moments, students will realize that
the potatoes’ high centers of mass make this task nearly impossible.
Center of mass
Point of
rotation
Center of mass
Next, have students apply their knowledge of center of mass by incorporating the forks in
the setup in such a way that the potato’s center of mass is lowered below the point of
rotation, (the eraser). This creates a remarkable stable system because a much greater
amount of rotation is required to bring the center of mass above the point of rotation.
Except in most extreme cases, the fork will rotate back into a state of equilibrium,
returning the center of mass to a position below the point of rotation.
When each group has successfully completed the experiment, have the entire class
discuss how they applied their knowledge on the center of mass to the balancing
problem. As an extension, have students experiment with the angle of the pencil. Is it
possible for them to balance the system with the pencil angled in various directions?
Discuss why different setups still create a balanced system. Once everyone has finished
the activity, ask the sumo wrestler to demonstrate some of his balance exercises for the
class. A common one is called shiko. It requires you to balance on one foot with your
other arm and leg outstretched. Have the class practice this move along with the wrestler
to give them an idea of how their center of mass changes when they spread out their
base and squat down low.
I do not think many of my students would have understood the concept of center of mass
as well if they had only read about in their text and answered the questions at the end of
the chapter. This activity gives insight in both the Japanese culture and important science
concept. This results in a decisive victory for the sensei (teacher).
For further reading:
Page 81
STRUCTURES STATION
•
•
MECHANICS
Hall, M., The Big Book of Sumo. Berkley: Stone Bridge Press, 1997.
Sakade, F., Peach Boy and Other Japanese Children’s Favorite Stories, Charles E. Tuttle
Company, Rutland, England, 1958.
Note: This research project was sponsored by the National Aeronautics and Space Administration
(NASA), Minority University Research, and Education Division.
Visit suggestions:
Bring these materials with you: stopwatch, tape measure.
Using the same number and type of pieces, see who can build:
•
the tallest structure that (without support from people or other objects) remains
upright for 30 seconds.
•
the tallest structure that (without support from people or other objects) remains
upright for 30 seconds while supporting an X-lb. object (choose the object / desired
weight).
•
a bridge that spans a specified distance (e.g. 2 ft).
•
a bridge that spans a specified distance while supporting an X-lb. object.
Sources:
Nave, Carl R. and Brenda C. Nave. Physics for the Health Sciences. 2nd ed. Philadelphia: W.B.
Saunders Company, 1980.
Page 82
STUNT FLYER
AIR / FLIGHT
Visitors modify Velcro®-covered rocket bodies by
attaching multiple wings and tails and then use
pressurized air to launch the rockets toward the
ceiling.
Text Panel:
“3...2...1...Liftoff!”
“It flew in a loop! How’d you do that?”
“By changing the pieces on these rockets, I can make them fly straight, or in a
loop or a spiral.”
“The air burst gives them thrust to overcome their weight. Then, the unequal
friction of drag on the angles of my wings, tails and canards* turn the plane,
making it turn in stunt patterns.”
“What stunts can you do?!”
*canard: a small projection like a wing near the nose of an aircraft, attached in order to create
extra horizontal stability (Source: Encarta® World English Dictionary©. Microsoft Corporation,
1999-2000)
The BIG Idea: Changing the body parts of the rocket affects its path of flight.
Four forces act on a plane in flight.
Lift
•
Lift is the force that helps keep the plane in the air.
Lift is generated when the wings of the
plane move through the air.
Drag
•
Weight is the force of gravity
pulling the plane toward the earth.
•
Thrust is the force that pushes the plane forward.
Weight
This may be generated by the exhaust exiting the
engines or by air moving through spinning propellers.
•
Drag is the force that slows down the plane’s forward motion.
Thrust
Aeronautical engineers may choose from among many types of wings when
designing a plane. Each wing type is best suited for specific flight requirements.
•
A Straight Wing gives the plane good lift at low speed, but increases the drag
Straight Wing
Sweepback
Forward Sweep
on the plane at high speed.
Page 83
Delta Wing
STUNT FLYER
•
•
•
AIR / FLIGHT
At high subsonic (less than the speed of sound) speeds, the Sweepback Wing
delays the formation of shock waves.
Forward Sweep wings reduce drag on the plane at transonic (close to the
speed of sound) speeds.
The Delta Wing is ideal for smooth supersonic (faster than the speed of
yaw
sound) flying.
Pilots are able to control their planes by manipulating moveable
parts (control surfaces) located on the tail and wings.
•
The rudder is found on the vertical portion of the tail. It helps
the pilot to control yaw
rotation.
pitch
•
The elevators are found on
rudder
the horizontal portions of the
tail
tail. They help the pilot to
wing
control the pitch of the plane.
elevators
•
The ailerons are found on
ailerons
the rear edges of the wings.
Moving the ailerons helps the
wing
pilot to control the roll of the plane.
Paper Rockets
http://www.grc.nasa.gov/WWW/K-12/TRC/Rockets/paper_rocket.html
(Sources: (1) “Paper ‘Rockets’.” Spacelog. Space Center, Alamogordo, NM. Vol. 12 #1 JanuaryMarch 1995: 5.
(2) Aerospace Education Services Project, Oklahoma State University – see website above.)
Objective: To demonstrate the importance of using control systems, such as fins, to
stabilize rockets in flight.
Description: In this activity, students construct small flying rockets out of paper and propel
them by blowing air through a straw.
Materials
• Scrap bond paper
• Cellophane tape
• Scissors
• Sharpened fat pencil
• Milkshake straw
(slightly thinner than a
pencil)
Procedure
• Cut a narrow rectangular strip of paper about 13 cm long and roll it tightly around a fat
pencil. Tape the cylinder and remove the pencil.
• Cut points into one end of the cylinder to make a cone and slip it back onto the pencil.
Page 84
roll
STUNT FLYER
•
•
•
AIR / FLIGHT
Slide cone end onto the pencil tip. Squeeze and tape together to seal the end and
form a nose cone (the pencil point provides support for taping). An alternative is just to
fold over one end of the tube and seal with tape.
Remove the cylinder from the pencil and gently blow into the open end to check for
leaks. If air easily escapes, use more tape to seal the leaks.
Cut out two sets of fins using the pattern and fold according to instructions. Tape the
fins near the open end of the cylinder. The tabs make taping easy.
Flying the paper rocket
• Slip the straw into the rocket's opening. Point the rocket in a safe direction and blow
sharply through the straw. The rocket will shoot away. (Caution: Be careful not to aim
the rocket towards anyone because the rocket could poke an eye.)
Discussion
The paper rocket activity demonstrates how rockets fly through the atmosphere. A rocket
with no fins is much more difficult to control than a rocket with fins. The placement and
size of the fins is critical to achieve adequate stability while not adding too much weight.
•
Just for the fun of it, try flying the paper rocket with the fins placed on the front end of
the cylinder. Also try attaching delta shaped wings to achieve a gliding flight. Can the
fins be made smaller and still stabilize the rocket? How many fins are required? Are
rocket fins necessary in outer space?
Control Surfaces
(Source: “The Science of Flight Part I.” Exploring Aeronautics. Print Materials, Section 1, 1998:
73-77. (see citation below))
Student Instructions
• Using a piece of paper of your choice, create a glider with control surfaces that work.
Then, adjust the control surfaces to perform the two stunts indicated on your
worksheet.
• For each maneuver, draw a diagram of your paper airplane in the box on the left and
color the control surfaces you used to perform the maneuver. Label the names of each
control surface. Then tell the position each one was in (up, down, left, right, etc.) In the
box on the right, draw its flight path. Use arrows to show the flight of your paper
airplane.
Below is an example of a roll to the left that pitches downward.
Airplane Diagram with
Control Surfaces
Flight Path
For each of the following draw both the airplane diagram with control surfaces and the
flight path (solutions shown):
Page 85
STUNT FLYER
AIR / FLIGHT
Maneuver 1: a loop-the-loop
Maneuver 2: a roll to the left that pitches upward
Maneuver 3: a roll to the right that pitches upward
Maneuver 4: a series of barrel rolls
Page 86
STUNT FLYER
AIR / FLIGHT
Visit suggestions:
Bring these materials with you: paper, pencils, rulers.
Have your students experiment at the Stunt Flyer exhibit, trying to build rockets that meet
certain criteria. For example, try to create a rocket that:
•
rolls to the left (right) and then pitches downward (upward).
•
flies in a complete loop.
•
spins about its axis as it moves.
Once a rocket has repeatedly met a specified goal, have the student draw a labeled
diagram of the rocket showing wing/ tail placements (rulers may be used to measure
distances from the rocket tip to the attached pieces) and a corresponding diagram
detailing the rocket’s flight path.
Sources:
Doser, Andrew, et al. Exploring Aeronautics. CD-ROM. National Aeronautics and Space
Administration, 1998 (NASA EC-1998-03-002-ARC).
Page 87
VELCRO® WALL
ANIMAL ADAPTATIONS
Visitors strap their hands onto Velcro®-covered
blocks and “walk” their hands up a carpet-covered
sloping wall.
Text Panel:
“Look! I’m The Fly Help meeee!”
“How are you sticking there?”
“I’m using Velcro®. A real fly has specially-adapted legs to do the same thing,
naturally.”
“Humans often get their ideas, like Velcro®, from the natural world.”
“Look at these hairs on the bottom of a fly’s feet, compared to this Velcro®*.
Walls that feel perfectly smooth to us actually have tiny bumps and cracks, used
as footholds by the tiny hairs.”
*See photos on following pages.
The BIG Idea: Organisms have unique features that allow them to maneuver in
their specific environments. Humans can study and copy these natural features to
suit other needs.
Background Information: Velcro® -like hooks are found in both the plant and
animal worlds.
Plants:
Some large seeds are covered in hooked
projections (burrs). During the germination
process, a seed provides food for the developing
plant. Large seeds have an advantage over
small ones because they contain more nutrients,
affording the new plant more time to become
established. Small seeds can be dispersed far
from the parent plant (where there is a higher chance of survival) more easily by
the wind than can large ones. Burrs on large seeds get caught in fur, feathers or
clothing and allow the seeds to be carried to distant locations where they can
develop into new plants.
Hook and Loop Fasteners:
A Swiss inventor named George de Mestral developed the hook and loop fastener
in the late 1940’s. Pulling prickly burrs off of his pant legs and his dog’s fur after
an outdoor walk, de Mestral became interested in discovering why the burrs were
Page 88
VELCRO® WALL
so difficult to remove. He
studied them under a microscope
and found that they consisted of
hundreds of curved projections
that could hook onto loops of
fabric or fur. He used this
concept to create hook and loop
tape, later known as genuine
Velcro® brand hook and loop
fasteners. (The word “Velcro” is
a combination of the French
words meaning “velvet hook” –
velours crochet.)
ANIMAL ADAPTATIONS
Velcro® Brand Hook and Loop Tape
magnified 35 times
Spiders and Flies
Many spiders and flies have natural hook-like features on their feet that allow
them to hold onto (what appear to be from the human perspective) smooth
surfaces. Some spiders have pads on the bottom of their feet (scopulae) that
contain dense hairs. These hairs hook into
the tiny irregularities found in all surfaces.
Various types of flies have adapted to
similar surroundings in different ways, and
some, like spiders, have tiny bristly hairs
on their feet that hook onto minute bumpy
projections.
Fly foot, magnified 300
The Insect World: Drawing Insect Adaptations
http://school.discovery.com/lessonplans/programs/insectworld/index.html
(Source: DeMary, John E. “The Insect World.” Lesson Plans Library > 6-8 Animals.)
Grade Level: 6-8
Procedure
Insects are well designed for the habitats in which they live. Divide the class into small
groups, and assign a specific habitat type to each group (e.g., salt marsh, lake, desert,
field, arctic tundra, deciduous forest, alpine meadow, or human residence). Have each
group create a designer insect, stressing creativity and evolution at its best. Have each
group list on paper a detailed description of its designer insect, explaining all the adaptive
features that help it to adapt well to its environment. Make sure the students provide a
scientific name (genus and species) for their insect that reflects some unique or
identifying quality of the organism. Ask students to draw their insect and present it to the
class.
Page 89
VELCRO® WALL
ANIMAL ADAPTATIONS
A few resources regarding different perspectives:
Have your students find satellite photos of Pittsburgh (or anywhere else) on the web site
www.terraserver.com. (If you need access to the Internet, your students can visit the Creative
Technology Center on Carnegie Science Center’s 3rd floor during your field trip. Note that this
may require a reservation.)
Obtain a copy of the book: Morrison, Philip and Phylis. Powers of Ten. New York: Scientific
American Library, W.H. Freeman and Co., 1982.
Obtain the film: Powers of Ten: A Film Dealing with the Relative Size of Things in the
Universe and the Effect of Adding Another Zero. Made by The Office of Charles & Ray
Eames, ©Charles & Ray Eames, 1977.
(Note: a 1968 version of the film also exists: A Rough Sketch for a Proposed Film Dealing
with the Powers of Ten and the Relative Size of Things in the Universe. Made by The Office of
Charles & Ray Eames.)
Visit suggestions:
Have your students think about / write about the world from another perspective:
Imagine that you are now the size of a fly (note: you have not turned into a fly – your
visual perception would be VERY different).
•
You are walking on a shag carpet. What does it look like from your perspective?
•
What does the surface of your ceiling look like?
•
Describe what it would be like to take a walk on a cement sidewalk. What objects
might you encounter? (gum, other insects, cracks, etc.) What would they look like to
you?
Imagine that you are now the same size as Mt. Washington (look out the window).
•
Describe what a piece of sandpaper would feel like to you.
•
What would Pittsburgh look like from this perspective?
Sources:
Encarta® World English Dictionary©. Microsoft Corporation, 1999-2000.
http://dictionary.msn.com
“Fly.” Microsoft® Encarta® Online Encyclopedia. 2000.
“housefly.” Encyclopædia Britannica. Encyclopædia Britannica Inc., 1999-2000.
http://www.britanica.com (Note: Site now requires a subscription to view full articles. 6/03)
“Re: How are insects …able to walk on the ceiling without falling…” The MAD Scientist
Network. ©1995-2000.
http://madsci.wustl.edu/posts/archives/dec98/914812190.Gb.r.html
Seeds of Life, The Wonderful World of Seeds
http://versicolores.ca/seedsoflife/ehome.html (Note: This site no longer exists. 6/03)
The Velcro Company
http://www.velcro.com
Page 90
BIBLIOGRAPHY
Apel, Willi, and Ralph T. Daniel. The Harvard Brief Dictionary of Music. New York: Pocket
Books, 1961.
Campbell, Neil A. Biology. California: The Benjamin/Cummings Publishing Co., Inc., 1987.
Doser, Andrew, et al. Exploring Aeronautics. CD-ROM. National Aeronautics and Space
Administration, 1998 (NASA EC-1998-03-002-ARC).
Company, 1986.
Gardner, Martin. aha! Insight. New York: Scientific American, Inc., 1978.
“Idea sheets.” school in the exploratorium. The Exploratorium, 3601 Lyon Street, San Francisco,
CA 94123, 1976.
Horowitz, Paul and Winfield Hill. The Art of Electronics. NY: Press Syndicate of the University
of Cambridge, 1985.
Hugh P. McCarthy, ed. Biological Science: A Molecular Approach. 4th ed. Lexington, MA: D.C.
Heath and Co., 1980.
“Magnetism and Electricity.” Module Overview, Grades 3-4. Full Option Science System. U.C.
Regents, University of California, 1992.
“Magnets and Motors” Student Activity Book, National Science Resources Center / Science and
Technology for Children. Smithsonian Institution - National Academy of Sciences, 1991.
Nave, Carl R. and Brenda C. Nave. Physics for the Health Sciences. 2nd ed. Philadelphia: W.B.
Saunders Company, 1980.
Nye, Bill, et al. Family Fun Science! Demo Tape, KCTS Television, 1998.
Polya, George. Mathematical Discovery, On Understanding, Learning, and Teaching Problem
Solving. New York: John Wiley & Sons, Inc., 1981.
Tool Box Science: Square Wheels…Driving Science Home. Ohio’s Center of Science and
Industry, 1994.
Walpole, Brenda. 175 Science Experiments to Amuse and Amaze Your Friends. New York:
Random House, 1988.
Weast, Robert C., Editor-in-Chief. CRC Handbook of Chemistry and Physics. 66th ed., Boca
Raton, FL: CRC Press, Inc., 1986
Page 91
WEB SITES
General Reference:
Encarta® World English Dictionary©. Microsoft Corporation, 1999-2000.
http://dictionary.msn.com
Encyclopædia Britannica, Inc. 1999-2000.
http://www.britanica.com
(Note: Site now requires a subscription to view full articles. 6/03)
Microsoft® Encarta® Online Encyclopedia. 2000.
General Science Information and Activities:
Exploratorium Snacks. The Exploratorium, 3601 Lyon Street, San Francisco, CA 94123.
Hartshorn, Robert L., et al. Physical Science Activities Manual. Center of Excellence for Science
and Mathematics Education at The University of Tennessee at Martin, Martin, TN, 1994.
How Stuff Works
http://www.howstuffworks.com
Jacobs, Steven. Whelmers. McREL’s Accessible Science Series, 1997.
http://www.mcrel.org/resources/whelmers/
The MAD Scientist Network
http://madsci.wustl.edu
NOVA Online
http://www.pbs.org/wgbh/nova
Please note: As of June 2003 when this manual was updated, all listed web sites were accessible
via the World Wide Web unless otherwise noted. Due to the unpredictable nature of the Internet,
the existence of these sites cannot be guaranteed after that time. In addition, while sites with
reputable sources were carefully chosen, Carnegie Science Center cannot be held responsible for
the content or accuracy of the information posted on these sites.
Page 92
CONNECTIONS TO NATIONAL EDUCATION STANDARDS: K-4
*An object's motion can be described by tracing and measuring its position over
time.
x
x
x
x
*The position and motion of objects can be changed by pushing or pulling.
* Sound is produced by vibrating objects. The pitch of the sound can be varied by
changing the rate of vibration.
x x
Velcro Wall
x
x
Stunt Flyers
x x x x
Structures Station
x
Strobes
x
Sound Delay Tube
*The position of an object can be described by locating it relative to another object
or the background.
Roller Ramps
x
Robotix Table
x x x
x
RiverScape
Rebound
PVC Pipes
Polygonapalooza
Plumb Crazy
Newton's Cradle
x
B: Physical Science: Properties of objects and materials *Objects are made of one
or more materials (and) can be described by the properties of the materials.
B: Physical Science: Position and motion of objects
Mobile Station
MarbleWorks
Laser Harp
Domino Station
Digital Drums
x
Circuit Table
Build-A-Critter
Animation Station
A: Science as Inquiry: Abilities necessary to do scientific inquiry.
Air Cannon
National Science Education Standard / National Math Standard
Animal Adaptations
Exhibit Module
x
x x
x
x
x
x
x
x
x
B: Physical Science: Light, heat, electricity, and magnetism
*Light travels in a straight line until it strikes an object. Light can be reflected by a
mirror, refracted by a lens, or absorbed…
x
*Electricity in circuits can produce light, heat, sound, and magnetic effects.
Electrical circuits require a complete loop through which an electrical current can
pass.
x
C: Life Science: The characteristics of organisms
*Organisms have basic needs…The world has many different environments, and
distinct environments support the life of different types of organisms.
*Each plant or animal has different structures that serve different functions.
x
x
x
x
x
x
C: Life Science: Life cycles of organisms
C: Life Science: Organisms and their environments *An organism's patterns of
behavior are related to the nature of that organism's environment.
E: Science and Technology: Abilities of technological design
x
x
Analyze characteristics and properties of two- and three-dimensional geometric
shapes and develop mathematical arguments about geometric relationships
Apply transformations and use symmetry to analyze mathematical situations
x
x
Use visualization, spatial reasoning, and geometric modeling to solve problems
Page 93
x
CONNECTIONS TO NATIONAL EDUCATION STANDARDS: 5-8
x x
x x x
x
x x
x
x
x
x
x
x
x
x
x x
Velcro Wall
Stunt Flyers
Structures Station
Strobes
Sound Delay Tube
Roller Ramps
Robotix Table
RiverScape
Rebound
x x x
PVC Pipes
Polygonapalooza
Plumb Crazy
Newton's Cradle
x
Mobile Station
MarbleWorks
Laser Harp
x
Domino Station
Digital Drums
x
Circuit Table
Build-A-Critter
Animation Station
Air Cannon
Animal Adaptations
Exhibit Module
B: Physical Science: Motions and forces
*(An object's motion) can be described by position, direction...and speed.
x
x
*An object that is not being subjected to a force will continue to move at a constant
speed and in a straight line.
*…Unbalanced forces will cause changes in the speed or direction of an object's
motion.
B: Physical Science: Transfer of energy
*Energy...is associated with heat, light, electricity, mechanical motion,
sound...Energy is transferred in many ways.
*Light interacts with matter by transmission, absorption, or scattering.
x
x x x x x
*Electrical circuits provide a means of transferring electrical energy when heat,
light, sound...are produced.
C: Life Science: Structure and function in living systems
x x
*Living systems at all levels of organization demonstrate the complementary
nature of structure and function.
*Specialized cells perform specialized functions in multicellular organisms.
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
C: Life Science: Regulation and behavior
*All organisms must be able to obtain & use resources, grow, reproduce,...while
living in a constantly changing external environment.
*Behavior is one kind of response an organism can make to an internal or
environmental stimulus.
*An organism's behavior evolves through adaptation to its environment. How (it)
moves, obtains food,...are based in (its) evolutionary history.
C: Life Science: Diversity and adaptations of organisms
*Biological evolution accounts for the diversity of species...Species acquire many
of their unique characteristics through biological adaptation.
x
x
x
Page 94
CONNECTIONS TO NATIONAL EDUCATION STANDARDS: 9-12
Velcro Wall
Stunt Flyers
Structures Station
Strobes
x x x
x
x
Sound Delay Tube
Roller Ramps
x x
Robotix Table
RiverScape
x x x
Rebound
PVC Pipes
Polygonapalooza
Plumb Crazy
Newton's Cradle
x
Mobile Station
MarbleWorks
Laser Harp
x
Domino Station
x
x
Digital Drums
x
x
Circuit Table
*Objects change their motion only when a net force is applied ...Whenever 1 object
exerts force on another, a force equal in magnitude/opposite in direction is exerted
on the first object.
*The electric force is a universal force that exists between any two objects.
Opposite charges attract while like charges repel.
*Gravitation is a universal force that each mass exerts on any other mass.
Build-A-Critter
B: Physical Science: Structure of atoms *Matter is made of minute particles called
atoms (that) are composed of even smaller components (that) have measurable
properties such as mass and electrical charge.
B: Physical Science: Structure and properties of matter *Solids, liquids, and gases
differ in the distances and angles between molecules or atoms and therefore the
energy that binds them together.
B: Physical Science: Motions and forces
Animation Station
Air Cannon
Animal Adaptations
Exhibit Module
x
x
x x x
x
x
x
x x
x
x
B: Physical Science: Conservation of energy
*The total energy of the universe is constant. Energy can be transferred
…However, it can never be destroyed.
*All energy can be considered to be either kinetic, which the energy of motion;
potential, which depends on relative position; or energy contained by a field…
B: Physical Science: Interactions of energy and matter *Waves, including sound
and seismic waves, waves on water, and light waves have energy and can transfer
energy when they interact with matter.
C: Life Science: Biological evolution *Species evolve over time.
C: Life Science: Behavior of organisms *Organisms have behavioral responses to
internal changes & external stimuli.
*Like other aspects of an organism’s biology, behaviors have evolved through
natural selection. Behaviors often have an adaptive logic when viewed in terms of
evolutionary principles.
x
x x x x x
x
x x
x
x
x x
x
x
x
x
x
x
x
x
x
x
x
Page 95
x
x
x
x
x

Exploration Station Educator Guide

Transcription

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