question

the position and velocity of the ball

answer

You throw a ball. Air resistance on the ball is negligible. Which of the following functions change with time as the ball flies through the air?
only the position of the ball
only the velocity of the ball
only the acceleration of the ball
the position and velocity of the ball
the position and the velocity and acceleration of the ball

question

Either press the gas or the brake pedal or turn the steering wheel.

answer

You are driving a car at 65 mph. You are traveling north along a straight highway. What could you do to give the car a nonzero acceleration?
Press the brake pedal.
Turn the steering wheel.
Either press the gas or the brake pedal.
Either press the gas or the brake pedal or turn the steering wheel.

question

the position and velocity and acceleration of the ball

answer

A ball is lodged in a hole in the floor near the outside edge of a merry-go-round that is turning at constant speed. Which kinematic variable or variables change with time, assuming that the position is measured from an origin at the center of the merry-go-round?
the position of the ball only
the velocity of the ball only
the acceleration of the ball only
both the position and velocity of the ball
the position and velocity and acceleration of the ball

question

B

answer

Which of the paths would the cannonball most likely follow if the cannon barrel is horizontal?
A
B
C
D

question

A constant downward acceleration

answer

Now the cannon is pointed straight up and fired. (This procedure is not recommended!) Under the conditions already stated (drag is to be ignored) which of the following correctly describes the acceleration of the ball?
A steadily increasing downward acceleration from the moment the cannonball leaves the cannon barrel until it reaches its highest point
A steadily decreasing upward acceleration from the moment the cannonball leaves the cannon barrel until it reaches its highest point
A constant upward acceleration
A constant downward acceleration

question

downward to the right

answer

Which direction best approximates the direction of a? when the object is at position 1?
straight up
downward to the left
downward to the right
straight down

question

straight up

answer

Which direction best approximates the direction of a? when the object is at position 2?
straight up
upward to the right
straight down
downward to the left

question

straight down

answer

Which direction best approximates the direction of a? when the object is at position 3?
upward to the right
to the right
straight down
downward to the right

question

A

answer

What is the direction of the acceleration of the object at moment 5?

question

directions at time step 0, time step 10 = D,F

answer

What is the direction of the acceleration of the object at moments 0 and 10?

question

The acceleration is perpendicular to v? A and directed toward the inside of the track.

answer

Let v? A be the velocity of the car at point A. What can you say about the acceleration of the car at that point?
The acceleration is parallel to v? A.
The acceleration is perpendicular to v? A and directed toward the inside of the track.
The acceleration is perpendicular to v? A and directed toward the outside of the track.
The acceleration is neither parallel nor perpendicular to v? A.
The acceleration is zero.

question

The acceleration is perpendicular to v? C and pointed toward the inside of the track.

answer

Let v? C be the velocity of the car at point C. What can you say about the acceleration of the car at that point?
The acceleration is parallel to v? C.
The acceleration is perpendicular to v? C and pointed toward the inside of the track.
The acceleration is perpendicular to v? C and pointed toward the outside of the track.
The acceleration is neither parallel nor perpendicular to v? C.
The acceleration is zero.

question

The acceleration is perpendicular to v? D and pointed toward the outside of the track.

answer

Let v? D be the velocity of the car at point D. What can you say about the acceleration of the car at that point?
The acceleration is parallel to v? D.
The acceleration is perpendicular to v? D and pointed toward the inside of the track.
The acceleration is perpendicular to v? D and pointed toward the outside of the track.
The acceleration is neither parallel nor perpendicular to v? D.
The acceleration is zero.

question

The acceleration is zero

answer

Let v? F be the velocity of the car at point F. What can you say about the acceleration of the car at that point?
The acceleration is parallel to v? F.
The acceleration is perpendicular to v? F and pointed toward the inside of the track.
The acceleration is perpendicular to v? F and pointed toward the outside of the track.
The acceleration is neither parallel nor perpendicular to v? F.
The acceleration is zero.

question

D, F

answer

Assuming that all cars have equal speeds, which car has the acceleration of the greatest magnitude, and which one has the acceleration of the least magnitude?

question

The magnitude of the acceleration of the car at point A is four times that of the car at point E.

answer

Assume that the car at point A and the one at point E are traveling along circular paths that have the same radius. If the car at point A now moves twice as fast as the car at point E, how is the magnitude of its acceleration related to that of car E.
The magnitude of the acceleration of the car at point A is twice that of the car at point E.
The magnitude of the acceleration of the car at point A is the same as that of the car at point E.
The magnitude of the acceleration of the car at point A is half that of the car at point E.
The magnitude of the acceleration of the car at point A is four times that of the car at point E.

question

v0 = v2 > v1 > 0

answer

How do the speeds v0, v1, and v2 (at times t0, t1, and t2) compare?
v0 = v1 = v2 > 0
v0 = v2 > v1 = 0
v0 = v2 > v1 > 0
v0 > v1 > v2 > 0
v0 > v2 > v1 = 0

question

15.0, 26.0, 0, -9.80

answer

Consider a diagram of the ball at time t0.(Figure 2) Recall that t0 refers to the instant just after the ball has been launched, so it is still at ground level (x0=y0=0m). However, it is already moving with initial velocity v? 0, whose magnitude is v0=30.0m/s and direction is ?=60.0degrees counterclockwise from the positive x direction.
What are the values of the intial velocity vector components v0,x and v0,y (both in m/s) as well as the acceleration vector components a0,x and a0,y (both in m/s2)? Here the subscript 0 means "at time t0."

question

15.0, 0, 0, -9.80

answer

Consider a diagram of the ball at time t0.(Figure 2) Recall that t0 refers to the instant just after the ball has been launched, so it is still at ground level (x0=y0=0m). However, it is already moving with initial velocity v? 0, whose magnitude is v0=30.0m/s and direction is ?=60.0degrees counterclockwise from the positive x direction.
What are the values of the velocity vector components v1,x and v1,y (both in m/s) as well as the acceleration vector components a1,x and a1,y (both in m/s2)? Here the subscript 1 means that these are all at time t1.

question

t1?t0
t2?t1
(t2?t0)/2

answer

The flight time refers to the total amount of time the ball is in the air, from just after it is launched (t0) until just before it lands (t2). Hence the flight time can be calculated as t2?t0, or just t2 in this particular situation since t0=0. Because the ball lands at the same height from which it was launched, by symmetry it spends half its flight time traveling up to the peak and the other half traveling back down. The flight time is determined by the initial vertical component of the velocity and by the acceleration. The flight time does not depend on whether the object is moving horizontally while it is in the air.
If a second ball were dropped from rest from height ymax, how long would it take to reach the ground? Ignore air resistance.
Check all that apply.
t0
t1?t0
t2
t2?t1
(t2?t0)/2

question

Increase v0 above 30 m/s.
Reduce ? from 60 degrees to 45 degrees.

answer

range: R=vxt2=v20sin(2?)/g
Which of the following changes would increase the range of the ball shown in the original figure?
Check all that apply.
Increase v0 above 30 m/s.
Reduce v0 below 30 m/s.
Reduce ? from 60 degrees to 45 degrees.
Reduce ? from 60 degrees to less than 30 degrees.
Increase ? from 60 degrees up toward 90 degrees.

question

The one fired from 60?

answer

Which projectile spends more time in the air, the one fired from 30? or the one fired from 60??
The one fired from 30?
The one fired from 60?
They both spend the same amount of time in the air

question

four times as far

answer

Consider the video you just watched. Suppose we replace the original launcher with one that fires the ball upward at twice the speed. We make no other changes. How far behind the cart will the ball land, compared to the distance in the original experiment?
the same distance
twice as far
four times as far
half as far
by a factor not listed above