Chapter 19 Resource: Force and Newton`s Laws

Transcription

Glencoe Science
Chapter Resources
Force and Newton’s Laws
Includes:
Reproducible Student Pages
ASSESSMENT
TRANSPARENCY ACTIVITIES
✔ Chapter Tests
✔ Section Focus Transparency Activities
✔ Chapter Review
✔ Teaching Transparency Activity
HANDS-ON ACTIVITIES
✔ Assessment Transparency Activity
✔ Lab Worksheets for each Student Edition Activity
Teacher Support and Planning
✔ Laboratory Activities
✔ Content Outline for Teaching
✔ Foldables–Reading and Study Skills activity sheet
✔ Spanish Resources
✔ Teacher Guide and Answers
MEETING INDIVIDUAL NEEDS
✔ Directed Reading for Content Mastery
✔ Directed Reading for Content Mastery in Spanish
✔ Reinforcement
✔ Enrichment
✔ Note-taking Worksheets
Glencoe Science
Photo Credits
Section Focus Transparency 1: Leroy Simon/Visuals Unlimited;
Section Focus Transparency 2: UNIVERSAL PRESS SYNDICATE;
Section Focus Transparency 3: Wally McNamee/CORBIS,
Teaching Transparency: (t) Globus Brothers Studios, New York, (b) Stone
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that such material be reproduced only for classroom use; be provided to students,
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1 2 3 4 5 6 7 8 9 10 079 09 08 07 06 05 04
Reproducible
Student Pages
Reproducible Student Pages
■
Hands-On Activities
MiniLAB: Try at Home Observing Friction . . . . . . . . . . . . . . . . . . . . . 3
MiniLAB: Measuring Force Pairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Lab: Balloon Races . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Lab: Design Your Own Modeling Motion in Two
Directions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Laboratory Activity 1: Static and Sliding Friction . . . . . . . . . . . . . . . . 9
Laboratory Activity 2: Newton’s Second Law . . . . . . . . . . . . . . . . . . . 13
Foldables: Reading and Study Skills. . . . . . . . . . . . . . . . . . . . . . . . . . 17
■
Meeting Individual Needs
Extension and Intervention
Directed Reading for Content Mastery . . . . . . . . . . . . . . . . . . . . . . . 19
Directed Reading for Content Mastery in Spanish . . . . . . . . . . . . . . 23
Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Enrichment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Note-taking Worksheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
■
Assessment
Chapter Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Chapter Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
■
Transparency Activities
Section Focus Transparency Activities . . . . . . . . . . . . . . . . . . . . . . . . 44
Teaching Transparency Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Assessment Transparency Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
1
Hands-On Activities
Hands-On
Activities
2 Force and Newton’s Laws
Date
Class
Hands-On Activities
Name
Observing Friction
Procedure
1. Lay a bar of soap, a flat eraser, and a key side by side on one end of a hard-sided notebook.
2. At a constant rate, slowly lift the end of the notebook with objects on it. Note the order in
which the objects start sliding. Record your observations in the table.
Data and Observations
Bar of Soap
Eraser
Key
Analysis
Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc.
1. For which object was static friction the greatest? For which object was it the smallest? Explain,
based on your observations.
2. Which object slid the fastest? Which slid the slowest? Explain why there is a difference in
speed?
3. How could you increase and decrease the amount of friction between the two materials?
3
Name
Date
Class
Procedure
1. Work in pairs. Each person needs a spring scale.
2. Hook the two scales together. Each person should pull back on a scale. Record the two
readings in the table below. Pull harder and record the two readings.
3. Continue to pull on both scales, but let the scales move toward one person. Do the readings
change?
4. Try to pull in such a way that the two scales have different readings.
Set-up
First pull
both partners
pull
Second pull
both partners
pull harder
Third pull
scales closer to
one person
Scale 1
Fourth pull
Fifth pull
Analysis
1. What can you conclude about the pair of forces in each situation?
2. Explain how this experiment demonstrates Newton’s third law.
Scale 2
Hands-On Activities
Measuring Force Pairs
Name
Date
Class
Hands-On Activities
Balloon Races
Lab Preview
Directions: Answer these questions before you begin the Lab.
1. What does Newton’s third law of motion state?
2. What will you use to make a path for your rocket?
The motion of a rocket lifting off the launch pad is determined by Newton’s
laws of motion. Here you will make a balloon rocket that is powered by
escaping air.
Real-World Question
How do Newton’s laws of motion explain the motion of balloon rockets?
Materials
balloons
drinking straws
meterstick
string
tape
stopwatch
*clock
*Alternate materials
Goals
■
■
Measure the speed of a balloon rocket.
Describe how Newton’s laws explain a rocket’s motion.
Safety Precautions
Procedure
1. Make a rocket path by threading a string
through a drinking straw. Run the string
across the classroom and fasten at both ends.
2. Blow up a balloon and hold it tightly at the
end to prevent air from escaping. Tape the
balloon to the straw on the string.
3. Release the balloon so it moves along the
string. Measure the distance the balloon
travels and the time it takes.
4. Repeat steps 2 and 3 with different balloons.
5
Name
Date
Class
(continued)
1. Compare and contrast the distances traveled. Which rocket went the greatest distance?
2. Calculate the average speed for each rocket. Compare and contrast them. Which rocket has the
greatest average speed?
Conclude and Apply
1. Infer which aspects of these rockets made them travel far or fast.
2. Draw a diagram on a separate sheet of paper showing all the forces acting on a balloon rocket.
3. Use Newton’s laws of motion to explain the motion of a balloon rocket from launch until it
comes to a stop.
Communicating Your Data
Discuss with classmates which balloon rocket traveled the farthest. Why? For more help,
refer to the Science Skill Handbook.
Hands-On Activities
Analyze Your Data
Name
Date
Class
Hands-On Activities
Design Your Own
Modeling Motion in Two Directions
Lab Preview
Directions: Answer these questions before you begin the Lab.
1. What is a net force?
2. What safety precautions must you take for this Lab?
When you move a computer mouse across a mouse pad, how does the rolling
ball tell the computer cursor to move in the direction that you push the
mouse? Inside the housing for the mouse’s ball are two or more rollers that
the ball rubs against as you move the mouse. They measure up-and-down
and back-and-forth motions. The motion of the cursor on the screen is based
on the movement of the up-and-down rollers and the back-and-forth rollers.
Real-World Question
Goals
Can any object be moved along a path by a
series of motions in only two directions?
■
Form a Hypothesis
How can you combine forces to move in a
straight line, along a diagonal, or around
corners? Place a golf ball on something that
will slide, such as a plastic lid. The plastic lid
is called a skid. Lay out a course to follow on
the floor. Write a plan for moving your golf
ball along the path without having the golf
ball roll away.
Possible Materials
masking tape
stopwatch
*watch or clock with a second hand
meterstick
*metric tape measure
spring scales marked in newtons (2)
plastic lid
golf ball
*tennis ball
■
■
Move the skid across the ground using two
forces.
Measure how fast the skid can be moved.
Determine how smoothly the direction can
be changed.
Safety Precautions
Test Your Hypothesis
Make a Plan
1. Lay out a course that involves two directions,
such as always moving forward or left.
2. Attach two spring scales to the skid. One
always will pull straight forward. One
always will pull to one side. You cannot
turn the skid. If one scale is pulling toward
the door of your classroom, it must always
pull in that direction. (It can pull with zero
force, if needed, but it can’t push.)
3. How will you handle movements along
diagonals and turns?
4. How will you measure speed?
*Alternate materials
7
Name
Date
Class
(continued)
Follow Your Plan
1. Make sure your teacher approves your plan
before you start.
2. Move your golf ball along the path.
3. Modify your plan, if needed.
4. Organize your data so they can be used
to run your course and write them on a
separate sheet of paper.
5. Test your results with a new route.
Analyze Your Data
1. What was the difference between the two routes? How did this affect the forces you needed to
use on the golf ball?
2. How did you separate and control variables in this experiment?
3. Was your hypothesis supported? Explain.
Conclude and Apply
1. What happens when you combine two forces at right angles?
2. If you could pull on all four sides (front, back, left, right) of your skid, could you move anywhere
along the floor? Make a hypothesis to explain your answer.
Communicating Your Data
Compare your conclusions with those of other students in your class. For more help,
refer to the Science Skill Handbook.
Hands-On Activities
5. Experiment with your skid. How hard do
you have to pull to counteract sliding friction
at a given speed? How fast can you accelerate?
Can you stop suddenly without spilling the
golf ball, or do you need to slow down?
6. Write a plan for moving your golf ball
along the course by pulling only forward or
to one side. Be sure you understand your
plan and have considered all the details.
Date
1
Laboratory
Activity
Class
Static and Sliding Friction
When two objects are in contact, the molecules on one surface can attract molecules on the other
surface. These surfaces are not smooth; small bumps and grooves exist. When one object slides over
the other, the surfaces catch and stick as these bumps and grooves nestle together. The force that
results between the surfaces is called friction. Many factors affect the force of friction, including the
materials the surfaces are made from, how smooth the surfaces are, and how hard the surfaces are
pressed together. For a block sliding on a level horizontal surface, the weight of the block pushes
the bottom surface of the block against the horizontal surface.
When an object is at rest, static friction must be overcome to move the object. When one object
is already sliding over another, sliding friction occurs. To keep the object moving, a force must be
applied that is equal to the sliding friction force.
Strategy
You will calculate coefficients of static and sliding friction.
You will compare static friction to sliding friction.
You will describe the effect of weight on the force of friction.
You will determine the effect of surface area on friction.
Materials
eye hook
set of masses
spring scale calibrated in newtons
wood block (about 5 cm ✕ 10 cm ✕ 26 cm)
Procedure
1. Screw the eye hook into the end of the
block. Weigh the wood block and eye hook
using the spring scale. Record the weight in
the table.
2. Lay the wood block on a flat surface as
shown in Figure 1.
3. Find the force required to move the block
from rest. Pull on the spring scale and
notice the highest reading that occurs
before the block moves. That is the static
friction force.
Figure 1
10 cm
26 cm
Eye hook
5 cm
Spring scale
9
Hands-On Activities
Name
Name
Date
Class
Laboratory Activity 1 (continued)
µ static =
8. Calculate the coefficient of sliding friction for
each of the trials using the equation below.
µ sliding = sliding friction force
weight
9. Graph the relationship between the weight
of the block and the force of static friction
in Graph 1. Also graph the relationship
between the force of sliding friction and
the weight of the block in Graph 1.
static friction force
weight
Table 1
Force of
static friction
Force of
sliding friction
Weight
of block
␮Static
␮Sliding
Area
of side
Hands-On Activities
4. Find the force required to keep the block
moving at a constant speed. As you pull on
the spring scale, the reading will not be
exact because the friction value will vary.
Make the best judgment you can for the
value of sliding friction. Record this
value in the table.
5. Repeat steps 3 and 4 with different weights
added on top of the friction block. Be sure
to record the new weight of the block and
its added weight.
6. Repeat steps 3 and 4 without masses added
and with the block resting on a side with a
different area.
7. Calculate the coefficient of static friction
for each of the trials using the following
equation.
Name
Date
Class
Graph 1
Hands-On Activities
Weight Versus Friction Force
2.5
Friction force (N)
2.0
1.5
1
0.5
0
0
1
2
3
4
5
6
Weight (N)
Questions and Conclusions
1. How did the addition of more weight affect the friction?
2. How did the change in surface area of the contact between the block and the table affect the
friction?
3. How did the force of friction depend on the weight of the block?
4. Compare the size of static friction and sliding friction.
11
Name
Date
Class
6. What happened to the coefficients of friction as the weight increased?
7. What happened to the coefficients of friction as the surface area of the contact increased?
8. Does the coefficient of sliding friction depend on the weight of the block? Explain.
9. Does the area of contact between objects make a difference in the friction forces? Explain how
you know.
10. If you are buying new tires for a car, would you prefer a high or a low coefficient of friction?
Strategy Check
Can you calculate coefficients of static and sliding friction?
Do you understand the effects of weight and surface area on the force of friction?
Hands-On Activities
5. What could be a source of error in this experiment?
Date
2
Laboratory
Activity
Class
Newton’s Second Law
Newton’s second law of motion deals with acceleration, which is how quickly something speeds
up or slows down. Acceleration depends on the mass of an object and the force pulling or pushing
it. One way to write Newton’s second law is force = mass ✕ acceleration. Another way to think of
Newton’s second law is that if the same force acts on two objects, the object with the greater mass
will accelerate more slowly.
Strategy
You will time the acceleration of a small toy car.
You will observe the effects of increasing mass on acceleration.
Materials
balance
large table
meterstick
modeling clay (about 300 g)
small toy car with free-spinning wheels
stopwatch
string or thread
tape
Procedure
1. Cut a piece of string or thread 110 cm long.
Tie a small loop in one end of the string.
2. Make a small ball of clay with a mass of
about 2.5 g. Attach this ball of clay to the
string by folding the clay around the loop.
The loop will prevent the clay ball from
falling off the string.
3. Divide the remaining clay into 40-g pieces.
4. Use your balance to measure the mass of
the toy car. Write the mass of the car in the
Data and Observations section.
Figure 1
Toy car
String
Tape
1m
Clay ball
13
Hands-On Activities
Name
Name
Date
Class
8. Release the car. Use a stopwatch to measure
the time it takes for the car to reach the
table edge.
9. Write the travel time in Table 1.
10. Repeat steps 8 and 9 two more times. Use
the data to calculate the average travel
time for the car.
11. Add one 40-g piece of clay to the top of
the car. Be careful that the clay does not
interfere with the car’s ability to roll freely.
12. Time three trips of the car. Record the
travel times, calculate the average time,
and record the average time in Table 1.
13. Repeat steps 11 and 12 until you have
timed the car carrying 160 g of clay.
Mass of car = ______ g
Table 1
Mass (g)
Total clay on
top of car
Travel Time (s)
Total car
and clay
0
40
80
120
160
Time 1
(T1)
Time 2
(T2)
Time 3
(T3)
Average time
(T1 ⫹ T2 ⫹ T3) / 3
Hands-On Activities
5. Use a meterstick to find a spot on the table
1 m from the edge. Mark it with a small
piece of tape. This spot will be the starting
point for the toy car during the experiment.
6. Put the front of the toy car at the starting point.
Hold the piece of string on the table so that the
clay ball is about 3 cm over the edge. Tape the
other end of the string to the front of the toy
car. Trim any excess string so that it does not
interfere with the car’s wheels. Check that your
setup is similar to that shown in Figure 1.
7. Pick someone in your group to be the timer,
someone to be the recorder, someone to hold
the toy car in place and release it, and someone to catch it as it falls off the table.
Name
Date
Class
Hands-On Activities
Total mass (g)
Graph 1
Average travel time (s)
Questions and Conclusions
1. Make a graph of total mass versus time in Graph 1.
2. Explain how your data support Newton’s second law of motion.
3. Why is it important to average three travel times for each one of the total masses?
4. What were some possible sources of error in this lab? In other words, what things might have
caused differences in travel time for the same mass?
15
Name
Date
Class
Strategy Check
Do you understand the effects of increasing mass in acceleration?
Can you relate force, mass, and acceleration?
Hands-On Activities
5. Use your graph to predict how much mass would be necessary to cause travel time of 15 s.
Test your prediction. What happened?
Name
Date
Class
Hands-On Activities
Directions: Use this page to label your Foldable at the beginning of the chapter.
Newton’s Three
Laws of Motion
First Law of Motion
Second Law of Motion
Third Law of Motion
This law connects force, acceleration, and mass. It states that an object
acted upon by a net force will accelerate in the direction of the force.
This law describes how an object moves when no net force is acting on
it. It states that unless a net force acts on it, an object at rest tends to
stay at rest and a moving object will continue moving in a straight line
with constant speed.
This law describes the connection between the object supplying the
force and the object receiving the force. It states that forces always act
in equal but opposite pairs.
17
Meeting Individual
Needs
Name
Date
Directed Reading for
Content Mastery
Class
Overview
Directions: Complete the concept map using the phrases listed below.
the direction of the force
a net force
an equal but opposite reaction
the first law
the second law
the third law
which states that an
object at rest or moving
at constant speed in
a straight path will
continue to do so until
acted upon by
which states that an
object acted
upon by a net force
will accelerate in
which states that for
every action there is
1.
2.
3.
Newton’s laws
of motion
Directions: In the space provided, write the number for Newton’s law of motion that best applies to the
conditions described.
4. A golf ball is motionless until it is hit by a golf club.
5. The golf club is swung in a northerly direction, and that is the direction
the ball travels.
6. When hit, the golf ball pushes back on the club with the same amount
of force that the club exerts on the ball.
19
Name
Date
Content Mastery
Section 1
Section 3
■
■
Class
Newton’s First Law
Newton’s Third Law
Directions: Identify which one of Newton’s laws applies in each case. Explain your answers.
1.
2.
Name
Date
Section 2
Content Mastery
Class
■
Directions: Write the correct term in the boxes in the puzzle. The boxed letters should spell the word that
completes Newton’s Second Law in item 9.
1
2
3
E
4
5
6
7
8
E
1. ______ exists between any two objects that have mass.
2. ______ occurs any time an object speeds up, slows down, or changes direction.
Fnet
3. In the formula a = m , Fnet stands for ______.
4. When you sit in a chair, it exerts ______ against you.
5. Force is measured in ______.
6. A gravitational ______ exists between you and every object in the universe.
Fnet
7. In the formula a = m , m stands for ______.
8. ______ describes how fast an object is moving and in what direction.
9. An object acted upon by a force will _____________ in the direction of the force.
21
Name
Date
Content Mastery
Class
Key Terms
Directions: Use the following terms to complete the sentences below.
normal force
net force
friction
second law
inertia
third law
force
acceleration
1. When more than one force is acting on an object, the
______ determines the motion of the object.
2. When you throw a ball, your hand applies ______ to the ball.
3. _____ is the force that brakes use to stop a car.
4. _____ tells how velocity changes.
5. If an object is placed on a flat surface, the _____ is
straight up and is equal to the weight of the object.
6. “Forces always act in equal but opposite pairs” is Newton’s
_____ of motion.
_____ describes the action.
8. The tendency of an object to remain at rest is called _____.
7. Every time you change your speed or direction, Newton’s
Nombre
Fecha
Lectura dirigida para
Dominio del contenidio
Clase
Sinopsis
Las fuerzas y las leyes de Newton
Instrucciones: Completa el mapa de conceptos usando las siguientes frases.
la dirección de la fuerza
una fuerza neta
una reacción igual, pero opuesta
la primera ley
la segunda ley
la tercera ley
establece que un cuerpo en
reposo o en movimiento a una
velocidad constante, en una
trayectoria recta, permanecerá
así a menos que una fuerza
actúe sobre él
establece que un
cuerpo sobre el cual
actúa una fuerza
neta, acelerará en
que establece que
por cada acción
existe
1.
2.
3.
Satisface las necesidades individuales
Las leyes de
movimiento de Newton
Instrucciones: En el espacio dado, escribe el número de la ley de movimiento de Newton que mejor se aplica a
las condiciones descritas.
4. Una pelota de golf está en reposo hasta que se golpea con un palo de golf.
5. El palo de golf se oscila en dirección norte y esa es la dirección en que
viaja la pelota.
6. Al golpearse, la pelota de golf empuja el palo con la misma cantidad de
fuerza que el palo ejerce sobre ella.
23
Nombre
Fecha
Sección 1
Sección 3
Clase
■
■
Primera ley de Newton
Tercera ley de Newton
Instrucciones: Identifica cuál de las leyes de Newton se aplica en cada ejemplo. Explica tus respuestas.
1.
24 Las fuerzas y las leyes de Newton
2.
Nombre
Fecha
Clase
Sección 2
■
Segunda ley de Newton
Instrucciones: Escribe el término correcto para cada definición. Las letras en las cajas numeradas verticalmente
deben contener la palabra que completa el nombre de las leyes de Newton.
1
2
3
4
5
6
7
8
9
O
1. Cuando te sientas en una silla la silla ______ contra ti.
2. Un cuerpo sobre el cual se ejerce una fuerza, se ______ en la dirección de la
fuerza.
3. Existe una fuerza gravitatoria entre ti y todos los objetos del ______.
4. ocurre siempre que un objeto aumenta su rapidez, la disminuye o cambia de
dirección
F
5. En la fórmula a = neta , la m representa ______.
m
6. Te dice con qué rapidez se mueve un objeto y en qué dirección.
F
7. En la fórmula a = neta , la F representa ______.
m
8. existe entre dos cuerpos cualquiera que tienen masa
9. La fuerza se mide en ______.
25
Nombre
Fecha
Clase
Términos claves
Instrucciones: Usa los siguientes términos para completar las oraciones.
fuerza normal
fuerza neta
fricción
segunda ley
inercia
tercera ley
fuerza
aceleración
1. Cuando más de una fuerza actúa sobre un cuerpo, el(la)
2. Cuando lanzas una pelota, tu mano aplica un(a) sobre la
pelota.
3. Es la fuerza que usan los frenos para detener el auto.
4. El(La) ______ te dice los cambios en velocidad.
5. Si un objeto se coloca sobre una superficie plana, el(la)
______ es directamente hacia arriba y es igual al peso del
objeto.
6. “Las fuerzas siempre actúan en pares iguales pero
opuestos” es la ______ ley del movimiento de Newton.
7. Cada vez que cambias tu rapidez o dirección, la ______
de Newton describe la acción.
8. La tendencia de un cuerpo a permanecer en reposo se
llama ______.
26 Las fuerzas y las leyes de Newton
______ determina el movimiento del cuerpo.
Name
Date
Reinforcement
15 2 11 3
6 11 15 7 10 13 11 14 4
14 1 12 5
7 12 1
9
5 15 6
2
7 11 10 15 13 13 3
2
1
3 12 9 15 2 11 8 13 2
13 3
4
8 10 9
4 11 3
4
2 12 8
10 8
2
3 13 2
5
8 12 10 8
15 9 11 9 14 8
6
4 13 5
9
6 12 12 9
9 10 11 3
3 11 2 14 3
8
7
5
3 14 12 14 6
9 15 2 11 10 11 6
6 12 4
8 12 7
8
7 11 2
9
9 13 12 4
3 10 1 14 7
2
3
8
5
8
5
3 15 9
4
8 11 4
1
1 12 9
2 10
Directions: Mark each statement below either true or false. For each true statement, fill in all the corresponding numbers in the box above. When you’re done, you’ll find an important word from this chapter.
1. When the net force is zero, the forces on an object are balanced.
2. If two forces are in the same direction, they cancel each other out.
3. Any time the forces are unbalanced, an object will remain at rest.
4. According to Newton’s first law of motion, an object at rest will stay at rest until a net
force acts upon it.
5. According to Newton’s first law of motion, an object moving at a constant speed in a
straight path will continue to do so until a net force acts upon it.
6. Friction brings most moving objects to a stop.
7. Friction will never speed up an object.
8. Galileo believed that the natural state of an object was to be at rest.
9. If you slide a bag of groceries along a countertop, you must first overcome rolling
friction.
10. Walking would be impossible without rolling friction.
11. Rolling friction always reduces the net force acting against an object’s motion to zero.
12. Sliding friction is caused by the attraction between the two surfaces.
13. If an object accelerates, a push or pull must be acting on it.
14. If an object is not moving, the net force working on it is zero.
15. Friction can be reduced but never eliminated.
16. The word in the puzzle is __________________________________________.
27
1
Class
Name
Date
2
Class
Reinforcement
Directions: Select the term from the following list that matches each description. Some terms will not be used.
a.
b.
c.
d.
16 N
–16 N
gravity
F = ma
e.
f.
g.
h.
F
a =m
normal forces
air resistance
F = m 9.8s2m
(
)
i.
j.
k.
l.
600 N
Newton’s second law of motion
terminal velocity
Newton’s first law of motion
1. acts against the direction of motion and gets larger as an object moves faster
3. An object acted upon by a net force will accelerate in the direction of that force.
4. the gravitational force on any object near Earth’s surface
5. the outward forces exerted by a surface
6. the speed an object reaches when the force of gravity is balanced by the force of air
resistance
7. What force must be applied to a 60-kg object to make it accelerate at 10 m/s2?
Directions: Study the illustration of the diver. Then identify each statement as true or false. If the statement is
false, change the word(s) in italics to make it true.
8. After the diver jumps forward from the diving board, the force of
gravity will accelerate the diver parallel to the direction of motion.
9. When the diver hits the water, the force of the water against her
body can stop it about five times faster than the pull of gravity that
accelerated it.
10. If the diver doesn’t have the correct form when she enters the water,
the force of the water can accelerate her speed.
11. Air resistance prevents the diver from moving in a straight line once
she jumps from the platform.
2. Force is equal to mass times acceleration.
Name
3
Date
Reinforcement
Class
Directions: Complete the table by naming the action and reaction forces in the following examples.
Example
Action force
Reaction force
1. A flying bird
2. Two bumper cars
collide
3. Holding your hand
out the window
of a moving car
4. Walking
5. Touching your
finger to your nose
Directions: Complete the following sentences using the correct terms or phrases.
6. Newton’s third law states, “For every action, there is an equal but ____________________.”
7. There is no ____________________ in time between the action and the reaction.
8. One reason it’s often easy to miss an action-reaction pair is because of the ____________________
of one of the objects.
9. Action-reaction forces are always the same ____________________ but are in
opposite ____________________.
10. When you swim in water, your arms push the water ____________________. The water
reacts by pushing ____________________ on your arms, causing your body to
accelerate ____________________.
Directions: Answer the following question using complete sentences.
11. How could the action force of a canoe moving through water be increased?
29
Name
Enrichment
Class
Gyroscopes
A gyroscope is a kind of top that spins
around a central axis. If you’ve ever seen a toy
gyroscope, you know it’s a spinning wheel that
can balance on a string or a fingertip. Even if
you tilt your finger out to the side, the gyroscope continues to spin. That’s because of
Newton’s first law—an object continues its
state of motion unless a force acts upon it.
Even though you are moving your finger, no
force is applied to the gyroscope so it continues its spin. In keeping with Newton’s first law,
a gyroscope always points in just one direction.
That’s why it looks as if it’s defying gravity.
Navigation by Gyroscope
But gyroscopes aren’t just toys; they’re used
in everything from boats to missile guidance
systems to the Hubble Space Telescope. Gyroscopes can be mounted on boats, airplanes,
telescopes, or other platforms so that when
the object moves, the gyroscope (which
continually points in the same direction)
detects changes in altitude. Altitude in this
case is defined as “the position of an aircraft or
spacecraft determined by the relationship
between its axes and the horizon or other
reference point.”
In other words, a gyroscope can tell when
something is going off course.
The Hubble Telescope uses six gyroscopes.
Three are used to keep the telescope pointing in
the right direction; the other three are spares.
The Hubble gyroscopes are the most accurate in
the world. An airplane usually uses three gyroscopes to help in navigation. Each one spins in a
different direction. When the plane changes
direction, one of the gyroscopes detects it. The
movement is measured by a magnetic sensor,
and the airplane’s navigator or pilot calculates a
new path for the airplane to follow.
Other Gyroscopes
Gyroscopic function is also used in race
cars and motorbikes. In race cars, for example,
the engine acts as a gyroscope. Mechanics
rotate the engine in one direction so that as
the car goes around the track, the engine
pushes the front of the car’s body down and
the back of the car’s body up. This helps the
car stay on the track. It’s truly amazing how
powerful gyroscopic effects can be.
Directions: Use textbooks, the library, or other resources to help you answer the following questions.
1. Restate Newton’s first law of motion in your own words.
2. How important do you think the three gyroscopes are to the Hubble Space Telescope? Explain.
3. Do gyroscopes defy gravity? Explain.
4. Name another well-known space project that uses gyroscopes to operate.
1
Date
Name
Enrichment
Class
Off to the Races
It’s Friday afternoon and all you can think
about during science is the upcoming go-cart
race. You and a friend have been working on
your entry for over two months. With race
weekend only a month away, there is still a lot
of work to be done.
Your friend comes over after school with a worried look on her face. She explains to you that
Eunice and Bert have designed an awesome cart
that no one could possibly beat. As the two of you
sit and mope, an idea springs into your head.
“Wasn’t the science teacher talking about
something that had to do with acceleration?
Yeah, it was something about Newton.”
Finally, you remember exactly what it was.
“Newton’s second law of motion states that
the acceleration of an object is directly
proportional to the force acting on it, and
inversely proportional to its mass.”
You look to your friend with a smile on
your face and tell her it is time to get to work.
You explain that by using Newton’s second law
of motion you can help make sure that your
go-cart is the fastest one at the races.
Newton’s second law of motion can be
force or a = .fnet .
written as acceleration = net
mass
m.
m
1. If your go-cart weighs 500 kg, what is the force you will have to apply to accelerate it at +1.5m/s2?
2. You discover that Eunice and Bert’s go-cart weighs 400 kg and will have a 675 N force acting on
it. How fast will it accelerate (to the nearest tenth)?
3. If you are able to decrease the mass of your go-cart by 15 percent, and the same force that was
applied in number 1 is applied, will your go-cart be able to beat Eunice and Bert’s? (Round
your answer to the nearest tenth.) Explain.
31
2
Date
Name
3
Date
Enrichment
Class
Jupiter Furniture Design
He continues to laugh and jokes about needing to lose weight as he gets another chair. All
of a sudden it hits you—your dad’s mass and
the gravity acting on it caused the chair to
collapse.
After dinner you dig out your science book
and get to work. You go directly to the section
on Newton’s laws of motion and refresh your
memory. It appears that Newton’s third law
will help you. It states that, “an action force
has an equal, but opposite, reaction force.”
On Earth, gravity is measured at 9.8m/s2
down. That means that when your dad sits in
a chair, he is applying a force equal to his mass
multiplied by the force of gravity. This can be
written as Force = Mass ✕ Gravity, or mg.
When you calculate the weight of an object,
you write your answer in newtons (N).
1. Your father used to weigh 484 N. What was his mass (to the nearest tenth)?
2. Your father gained 30 N, which caused his chair to break. What was his new mass? How much
force was acting on the chair? How much force was reacting?
3. How much force will your father exert on Jupiter? (Jupiter’s gravity is 24.5m/s2.)
4. What will be the reaction force necessary to hold your father up and keep his chair from
collapsing on Jupiter?
5. Explain what these problems have to do with Newton’s third law.
Your mother works for NASA and has told
you that we are very close to colonizing
Jupiter. She tells you this is top secret and that
you shouldn’t tell anyone else. You always have
been an entrepreneur and immediately begin
thinking about ways you could profit from the
newly divulged information.
As you sit at your desk and stare around
your bedroom, you realize that furniture will
be needed if people are going to colonize
Jupiter. As quickly as your excitement builds,
however, it disappears. You are certain that
there are enough furniture designers in the
world already.
Your father comes home and calls you to
come down for dinner. As your dad sits in his
chair, it collapses to the floor. Everyone in the
family begins to laugh, including your father.
Name
Date
Note-taking
Worksheet
Section 1
Class
A. ______________—push or pull on an object
1. The combination of all the forces acting on an object is the ____________ force.
2. When forces are _________________ forces, they cancel each other out and do not change an
B. Newton’s __________________ of motion—an object will remain at rest or move with
constant speed unless a net force is applied.
C. _________________ is a force that resists sliding between two touching surfaces or through
air or water.
1. Friction ___________________ an object’s motion.
2. _______________ friction—the type of friction that prevents an object from moving when
a force is applied
3. ________________ friction is due to the microscopic roughness of two surfaces; it slows
down a sliding object.
4. ________________ friction between the ground and a wheel allows the wheel to roll.
Section 2
A. Newton’s ___________________ of motion connects force, acceleration, and mass; it explains
that an object acted upon by a force will accelerate in the direction of the force; acceleration
equals net force divided by mass.
B. ________________—attractive force between two objects; depends on the mass of the objects
and distance between them; gravitational force is also called _______________.
C. The second law explains how to __________________ the acceleration of an object if its mass
and the forces acting on it are both known.
D. In circular motion, the ____________________ force is always perpendicular to the motion.
E. The __________________________ is reached when the force of gravity is balanced by air
resistance; the size of the air resistance force depends on the shape of an object and its speed.
33
object’s motion; when forces are ___________________ forces, the motion of an object changes.
Name
Date
Class
Note-taking Worksheet (continued)
F. An object can speed up, slow down, or turn in the direction of the net force
when __________________ forces act on it.
Section 3
A. Newton’s __________________ of motion states that forces always act in equal but opposite
pairs; for every action there is an equal and opposite reaction.
B. Action-reaction forces are always the same size but are in _________________ directions and
1. When the mass of one object is considerably _______________ than the mass of another
object, the action-reaction force is not noticeable.
2. ____________ and ______________ exert action-reaction forces with objects such as
hands or canoe paddles.
3. A _______________ launches due to the equal but opposite forces of the burning fuel.
act on different objects.
Assessment
Assessment
Name
Date
Chapter
Review
Class
Part A. Vocabulary Review
Directions: Match the terms in Column II with the descriptions in Column I. Write the letter of the correct term
in the blank at the left.
Column I
Column II
1. An object at rest or moving at a constant speed in a
straight path will continue to do so until a net force
acts on it.
a. Newton’s first law
of motion
b. unbalanced forces
2. An object acted upon by a net force will accelerate in the
direction of the force according to the equation
force .
acceleration = netmass
c. balanced forces
d. friction
3. the outward force from a surface
e. net force
4. a push or a pull
f. normal force
5. The net forces on an object are not zero.
7. Forces always act in equal but opposite pairs.
8. two or more forces whose effects cancel each other
h. force
9. the rubbing force that acts against motion between two
touching surfaces
i. Newton’s second
law of motion
Assessment
g. Newton’s third law
of motion
6. the total force felt by an object
Directions: Complete the following sentences using the terms listed below. Some terms may not be used.
accelerate
sliding
brake
friction
slipping
velocity
wheel
inertia
static
strength
terminal velocity
10. An object will ____________________ when the net force is not zero.
11. ____________________ will never speed up an object.
12. The friction that prevents an object from moving when a force is applied is
____________________ friction.
13. The friction that slows down an object that slides is ____________________ friction.
14. A(n) ____________________ helps reduce sliding friction.
15. Normal force is supplied by the ____________________ of the surface.
37
Name
Date
Class
Chapter Review (continued)
16. The speed an object reaches when the force of gravity is balanced by the force of air resistance
is called ____________________.
17. Earth has so much ____________________ that it hardly accelerates when you push against
the ground while walking.
Part B. Concept Review
Directions: Correctly complete each sentence by underlining the best of the three choices in parentheses.
1. (Static, Sliding, Rolling) friction keeps an object at rest.
2. A force can (push, pull, either push or pull).
3. The unbalanced force that stops almost everything is (gravity, friction, momentum).
4. An object will accelerate in the direction of the (net force, balanced forces, normal force).
5. A net force acting on an object changes the object’s (mass, size, motion).
6. Newton’s (third, second, first) law of motion describes the connection between an object
supplying force and the object receiving the force.
7. A force in the opposite direction to the motion of the object will cause the object to
(speed up, slow down, turn).
Assessment
Directions: Answer the following questions using complete sentences.
9. Explain why it is easy to miss an action-reaction pair. Give an example.
10. Why does friction never speed up an object?
8. If an object is at rest, all forces acting on that object must be (unbalanced, balanced, normal).
Transparency
Activities
43
Name
1
Date
Section Focus
Transparency Activity
Class
Another Cup, Please
1. What causes the cup to break when it strikes the floor?
2. Why do the pieces eventually stop moving?
3. What determines how far and in what direction the coffee cup
(and coffee) will travel?
Little things happen every day that we don’t really think about. If a
cup of coffee gets knocked off a table, we grab a towel or a mop to
clean up the mess. But what if we looked at the event closely? There’s
a lot to be learned from even the most common occurrences.
Name
2
Date
Section Focus
Class
Loop D’loop
Have you ever gone upside down on a roller coaster? What kept the
car on the track? In the cartoon, Calvin is pulling the sled far up the
hill so he can get a good start.
1. Does it make a difference where Calvin begins his descent?
Explain.
2. How does friction figure into Calvin’s scheme?
3. How will gravity affect Calvin if he makes it into the loop?
CALVIN AND HOBBES © Watterson.
Reprinted with permission of UNIVERSAL PRESS SYNDICATE. All rights reserved.
45
Name
3
Date
Section Focus
Class
Pushing the Limits
1. When you run, in which direction does your body exert force?
2. How does friction help a runner?
3. How will this athlete stop at the end of the sprint?
People run for many reasons. Sometimes it’s for exercise or
competition, and sometimes it’s for the pure joy of running. Whatever the reason, running is about applied forces.
Date
1
Teaching Transparency
Activity
Name
Class
Newton’s Laws of Motion
47
Name
Teaching Transparency Activity
Date
Class
(continued)
1. What is force?
2. What is a balanced force?
3. In the top picture on the transparency, what is the club doing to the ball?
4. Describe Newton’s law of motion that explains the dynamics behind the rocket engine (middle
image on the transparency).
5. The girl pushing the sled is illustrating which of Newton’s laws of motion?
6. What unbalanced force brings nearly everything to a stop?
Name
Date
Assessment
Class
Directions: Carefully review the diagram and answer the following questions.
A
B
C
D
2. Rolling friction pushes on an object that is rolling. According to
this definition, which of these examples shows rolling friction?
F A and D
G B and A
H C and B
J D and C
3. A force is a push or pull. Which force is acting on all of the objects
in the diagram?
A Static friction
B Magnetism
C Gravity
D Acceleration
1. All of these objects have unbalanced forces acting upon them
EXCEPT ___.
AA
BB
CC
DD
49

Chapter 19 Resource: Force and Newton`s Laws

Transcription

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