Name:    Practice Quiz: Chapter 8 (Momentum)

Multiple Choice
Identify the choice that best completes the statement or answers the question.
net momentum before = net momentum after

1

A 4.0-kg ball has a momentum of 20.0 kg·m/s. What is the ball's speed?
 a. 80.0 m/s b. 20.0 m/s c. 0.2 m/s d. 5.0 m/s e. none of the above

2

The reason padded dashboards are used in cars is that they
 a. increase the time of impact in a collision. b. look nice and feel good. c. decrease the momentum of a collision. d. decrease the impulse in a collision. e. increase the force of impact in a collision.

3

The momentum of an object is defined as the object's
 a. velocity times the time interval. b. force times the time interval. c. mass times its velocity. d. mass times it acceleration. e. force times its acceleration.

4

A collision is considered elastic if
 a. after the collision, the objects have the same shape as before the collision. b. the objects that collide don't get warmer. c. the objects don’t stick together. d. there is no lasting deformation. e. all of the above

5

A 3-kg ball is thrown at 7 m/s. What is the ball's momentum?
 a. 7 kg·m/s b. 49 kg·m/s c. 21 kg·m/s d. 3 kg·m/s e. none of the above

6

A cannon recoils from launching a cannonball. The speed of the cannon's recoil is small because the
 a. impulse on the cannon is less than the impulse on the cannonball. b. force against the cannon is relatively small. c. cannon has far more mass than the cannonball. d. momentum of the cannon is unchanged. e. none of the above

7

The white ball below strikes the black 8-ball below traveling at 3 m/s. Assuming that each of the balls has the same mass, what is the velocity of the 8-ball after the collision?
 a. 3 m/s c. 1 m/s b. 6m/s d. 0 m/s

8

A ball is moving at 6.0 m/s and has a momentum of 24.0 kg·m/s. What is the ball's mass?
 a. 0.3 kg b. 24.0 kg c. 144.0 kg d. 4.0 kg e. none of the above

9

A 50-kg child on a skateboard is traveling at 7.0 m/s.  What is the resultant momentum?
 a. 350 kg·m/s b. 0.14 kg·m/s c. 50 kg·m/s d. 350 kg·m/s

10

The momentum change of an object is equal to the
 a. force acting on it times its velocity. b. object's mass times the force acting on it. c. force acting on it. d. velocity change of the object. e. impulse acting on it.

11

A 8-kg ball is thrown at 5 m/s. What is the ball's momentum?
 a. 25 kg·m/s b. 8 kg·m/s c. 5 kg·m/s d. 40 kg·m/s e. none of the above

12

When these two freight cars of different mass collide and couple, what will be their resultant velocity?

 a. 10 m/s b. 1.0 m/s c. 2 m/s d. 50 m/s

13

A cannonball shot from a long-barrel cannon travels faster than one shot from a short-barrel cannon because the cannonball receives a greater
 a. impulse. b. force. c. both A and B d. neither A nor B

14

If the momentum of an object changes and its mass remains constant,
 a. its velocity is changing. b. there is a force acting on it. c. it is accelerating (or decelerating). d. all of the above e. none of the above

15

Momentum of a system is conserved only when
 a. there is no net external force acting on the system. b. the system has zero momentum. c. the system is not moving. d. there are no forces acting on the system. e. there are no internal forces acting on the system.

16

A cannon fires a cannonball. The speed of the cannonball will be the same as the speed of the recoiling cannon
 a. because velocity is conserved. b. because both velocity and momentum are conserved. c. because momentum is conserved. d. if the mass of the cannonball equals the mass of the cannon. e. none of the above

17

A table tennis ball launcher is fired. Compared to the force on the ball, the force on the launcher is
 a. the same. b. smaller. c. larger.

18

A ball is moving at 7.0 m/s and has a momentum of 49.0 kg·m/s. What is the ball's mass?
 a. 7.0 kg b. 0.1 kg c. 49.0 kg d. 343.0 kg e. none of the above

19

Compared to a sports car moving at 30 miles per hour, the same sports car moving at miles per hour has
 a. twice as much momentum. b. four times as much momentum. c. the same momentum.

20

A 2.0-kg ball has a momentum of 6.0 kg·m/s. What is the ball's speed?
 a. 0.3 m/s b. 3.0 m/s c. 12.0 m/s d. 6.0 m/s e. none of the above

21

Which has more momentum, a large truck moving at 30 miles per hour or a small truck moving at 30 miles per hour?
 a. The large truck b. Both have the same momentum. c. The small truck