Chapter 3 - SFA Physics

Transcription

Chapter 3 - SFA Physics
```Chapter 3
Nonlinear Motion
1. MOTION IS RELATIVE
Example: Motion of a boat with respect to the
ground and with respect to the river.
Velocity of river
Velocity of boat with respect to river
Add the velocity of the river
Velocity of boat with respect to ground
Velocity of river
Velocity of boat with respect to river
Add the velocity of the river
Velocity of boat with respect to ground
Velocity of boat with respect to ground
Velocity of river
Velocity of boat with respect to river
2.
VELOCITY - A VECTOR
QUANTITY
Scalars are quantities that are specified by
magnitude only.
 Examples: distance, time, mass, density
 Vectors are quantities that are specified by
magnitude and direction.
 Examples: displacement, velocity,
acceleration, force, momentum, angular
momentum

The Displacement Vector
What is the displacement
for this trip?
5 miles
370 north of east
4 miles east
3 miles north
3. PROJECTILE MOTION

Projectile motion is a combination of
vertical free-fall motion and horizontal
motion at a constant speed.
Parabola (approximately)

Demo - Ball projector and dropper

Demo - Monkey in tree

Demo - Cart and ball launcher

Demo - Wall parabola
The free-fall motion of a projectile near the surface
of the earth is very nearly parabolic.
A parabola is one of the of a conic sections.
Circle
Ellipse
Parabola
Hyperbola
For a particular range less than the maximum
and for a particular launch velocity,
two different launch angles will give that range.
The two angles add to give 900.
450 gives the maximum range.
Simulation
Free Fall Results
Horizontal motion is constant
 Vertical Motion is accelerated
 Rise time = Fall Time
 Final speed = Initial speed


Actual path and ideal path (free fall) are
different.
4.
FAST-MOVING PROJECTILES SATELLITES

Lets throw stones horizontally with ever
increasing velocity.

The Earth’s curvature is 16 ft for every 5 miles
(4.9 m for 8 km).
Throw an object faster, faster, faster.
5 miles
16 ft
We draw in each trajectory for 1 second
Vescape = 7 mi/s = 11 km/s
Vcircle = 5 mi/s = 8 km/s
Ellipse
Ellipse
Ellipse - Circle
Ellipse
Ellipse
4. CIRCULAR MOTION
Linear speed and rotational speed

Linear speed is a distance divided by time.

Rotational speed is an angle measurement
divided by time.
Two Flies on a Turntable
Which fly has the
greater rotational speed?
Which fly has the
greater linear speed?
B
Same for both.
A
B
Chapter 3 Review Questions
A rock is thrown upward at an
angle. What happens to the
horizontal component of its
velocity as it rises? (Neglect air
resistance.)
(a) it decreases
(b) it increases
(c) it remains the same
In the game of baseball which
path would a home run most
closely approximate? (Neglect
air resistance.)
(a) hyperbolic
(b) parabolic
(c) eccentric
A projectile is launched upward at an
angle of 75o from the horizontal and
strikes the ground a certain distance
down range. What other angle of launch
at the same launch speed would produce
the same distance? (Neglect air
resistance.)
(a) 450
(b) 150
(c) 250
A horizontally traveling car drives off of
a cliff next to the ocean. At the same
time that the car leaves the cliff a
bystander drops his camera. Which hits
the ocean first? (Neglect air resistance.)
(a) car
(b) camera
(c) they both hit at the same time
Bug A is 3 inches from the center of a
rotating 33.33 rpm record. Bug B is 5
inches from the center of the same
record. Bug A has
linear speed
and
rotational speed as bug B.
(a) less, less
(b) less, same
(c) same, less
(d) same, same
(e) less, greater
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