# Units 4 Review

Momentum

1. Which of the following objects have momentum?

a. an electron orbitting the nucleus of an atom.

b. a UPS truck stopped in front of the school building.

c. a compact car moving with a constant speed.

d. a flea moving with constant speed.

e. Glenbrook South High School.

Momentum (7 seconds)

2. A freight train rolls along a track with considerable momentum. If it rolls at the same speed but has twice as much mass, its momentum is ________________.

 a. zero b. quadrupled c. doubled d. unchanged

Momentum (7 seconds)

3. Impulses are smaller when bounces take place.

 a. True b. False

Real-World Applications (15 seconds)

4. A karate expert executes a swift blow and severs a cement block with her or his bare hand. The

1. impulse on both the block and the expert's hand have the same magnitude.
2. force on both the block and the expert's hand have the same magnitude.
3. time of impact on both the block and the expert's hand is the same.
4. all of the above.
5. none of the above.

Momentum Conservation Principle (16 seconds)

5. A rocket cannot accelerate in outer space because ...

1. there is no air in space
2. there is no friction in space
3. there is no gravity in outer space
4. both a and b
5. ... nonsense! Rockets do accelerate in outer space.

The Law of Action-Reaction (Revisited) (8 seconds)

6. In order to catch a ball, a baseball player moves his or her hand backward in the direction of the ball's motion. Doing this reduces the force of impact on the players hand principally because ...

1. the resultant velocity of impact is lessened.
2. the momentum change is reduced.
3. the time of impact is increased.
4. the time of impact is decreased.
5. none of these.

Real-World Applications (15 seconds)

7. Paul D. Trigger fires a bullet. The speed of the bullet will be the same as the speed of the recoiling gun ______________.

1. because momentum is conserved
2. because velocity is conserved
3. because both velocity and momentum are conserved
4. only if the mass of the bullet equals the mass of the gun
5. none of these

The Law of Action-Reaction (Revisited) (8 seconds)

8. You're driving down the highway and a bug spatters into your windshield. Which undergoes the greater change is momentum?
 a. the bug b. your car c. both the same

Momentum Conservation Principle (16 seconds)

9. You're driving down the highway and a bug spatters into your windshield. Which undergoes the greater force?
 a. the bug b. your car c. both the same

Momentum Conservation Principle (16 seconds)

10. You're driving down the highway and a bug spatters into your windshield. Which undergoes the greater impulse?
 a. the bug b. your car c. both the same

Momentum Conservation Principle (16 seconds)

11. You're driving down the highway and a bug spatters into your windshield. Which undergoes the greater acceleration?
 a. the bug b. your car c. both the same

Momentum Conservation Principle (16 seconds)

12. Three books, X, Y, and Z, rest on a table as shown in the diagram at the right. The weight of each book is indicated. The net or unbalanced force acting on book Y is

 a. 4 N down. b. 5 N down. c. 5 N up. d. 10 N up. e. zero.

Net Force (9 seconds)

13. Two identical freight cars roll without friction towards each other on a level track. One rolls at 2 m/s and the other rolls at 1 m/s. After the cars collide, they couple (attach together) and roll together with a speed of _____________.
 a. 0.5 m/s b. 0.33 m/s c. 0.67 m/s d. 1.0 m/s e. none of these

Momentum Conservation Principle (16 seconds) | Using the Momentum Equation as a Guide to Thinking (19 seconds)

14. A freight train rolls along a track with considerable momentum. If it rolls at the same speed but has twice as much mass, its momentum is ____.
 a. zero b. quadrupled c. doubled d. unchanged

Using the Momentum Equation as a Guide to Thinking (19 seconds)

15. A rifle recoils from firing a bullet. The speed of the rifle's recoil is small because the ___.
 a. force against the rifle is relatively small. b. speed is mainly concentrated in the bullet. c. rifle has lots of mass. d. momentum of the rifle is unchanged. e. none of these.

Momentum Conservation Principle (16 seconds) | Momentum Conservation in Explosions (12 seconds)

16. Two objects, A and B, have the same size and shape, but A is twice as heavy as B. When they are dropped simultaneously from a tower (in the absence of air resistance), they reach the ground at the same time, but A has a higher ___.
 a. speed b. acceleration c. momentum d. all of the above e. none of the above

The Acceleration of Gravity (5 seconds) | Momentum (7 seconds)

17. Padded dashboards in cars are safer in an accident than non-padded ones because they ____.
 a. increase the impact time. b. decrease an occupant's impulse. c. decrease the impact force d. two of the above e. none of the above.

Real-World Applications (15 seconds)

18. A 4 kg ball has a momentum of 12 kg*m/s. The ball's speed is ___ m/s.
 a. 3 b. 4 c. 12 d. 48 e. none of these.

Momentum (7 seconds)

19. A piece of putty moving with 1 unit of momentum strikes and sticks to a heavy bowling ball that is initially at rest. After the putty sticks to the ball, both are set in motion with a combined momentum that is ___.
 a. less than 1 unit b. more than 1 unit c. 1 unit d. not enough information

Momentum Conservation Principle (16 seconds)

20. A large force acting for a long amount of time on a small mass will produce a ______.
 a. small velocity change b. large velocity change c. small momentum change d. small acceleration e. two of the above

Momentum and Impulse Connection (14 seconds) | Real-World Applications (15 seconds)

21. Force and time pertains to momentum change in the same manner as force and distance pertains to ___________.
 a. impulse b. work c. energy change d. velocity e. none of these.

Momentum and Impulse Connection (14 seconds) | Analysis of Situations Involving External Forces (21 seconds)

22. A 5-N force is applied to a 3-kg object to change its velocity from +9 m/s to +3 m/s. The momentum change of the object is:
 a. -2.5 kg*m/s b. -10 kg*m/s c. -18 kg*m/s d. -45 kg*m/s e. none of these

Momentum and Impulse Connection (14 seconds)

23. A 5-N force is applied to a 3-kg object to change its velocity from +9 m/s to +3 m/s. The impulse experienced by the object is:
 a. -2.5 N*s b. -10 N*s c. -18 N*s d. -45 N*s e. none of these

Momentum and Impulse Connection (14 seconds)

24. A 5-N force is applied to a 3-kg object to change its velocity from +9 m/s to +3 m/s. The impulse acts for a time period of
 a. 1.8 s b. 2.5 s c. 3.6 s d. 10 s e. none of these

Momentum and Impulse Connection (14 seconds)

25. When a mass M experiences a velocity change of v in a time of t, it experiences a force of F. Assuming the same velocity change of v, the force experienced by a mass of 2M in a time of (1/2)t is
 a. 2F b. 4F c. (1/2)*F d. (1/4)*F e. none of these

Momentum and Impulse Connection (14 seconds) | Real-World Applications (15 seconds)

26. When a mass M experiences a velocity change of v in a time of t, it experiences a force of F. Assuming the same velocity change of v, the force experienced by a mass of 2M in a time of (1/4)t is
 a. 2F b. 8F c. (1/2)*F d. (1/8)*F e. none of these

Momentum and Impulse Connection (14 seconds) | Real-World Applications (15 seconds)

27. When a mass M experiences a velocity change of v in a time of t, it experiences a force of F. Assuming the same velocity change of v, the force experienced by a mass of (1/2)M in a time of (1/2)t is
 a. 2F b. 4F c. (1/2)*F d. (1/4)*F e. none of these

Momentum and Impulse Connection (14 seconds) | Real-World Applications (15 seconds)

28. When a mass M experiences a velocity change of v in a time of t, it experiences a force of F. Assuming the same velocity change of v, the force experienced by a mass of (1/2)M in a time of 4t is
 a. 2F b. 8F c. (1/2)*F d. (1/8)*F e. none of these

Momentum and Impulse Connection (14 seconds) | Real-World Applications (15 seconds)

29. A 0.5-kg ball moving at 5 m/s strikes a wall and rebounds in the opposite direction with a speed of 2 m/s. If the impusle occurs for a time duration of 0.01 s, then the average force (magnitude only) acting upon the ball is
 a. 0.14 N b. 150 N c. 350 N d. 500 N e. none of these

Momentum and Impulse Connection (14 seconds)

30. If mass and collision time are equal, then impulses are greater on objects which rebound (or bounce).
 a. TRUE b. FALSE

Effect of Rbounding (15 seconds)

31. An unfortunate bug strikes the windshield of a bus in a head-on collision. Which of the following statements are true?

1. The magnitude of the force encountered by the bug is greater than that of the bus.
2. The magnitude of the impulse encountered by the bug is greater than that of the bus.
3. The magnitude of the momentum change encountered by the bug is greater than that of the bus.
4. The magnitude of the velocity change encountered by the bug is greater than that of the bus.
5. The magnitude of the acceleration encountered by the bug is greater than that of the bus.

The Law of Action-Reaction (Revisited) (8 seconds)

### Problem-Solving:

32. A 0.80-kg ball strikes a wall moving at 5.0 m/s and rebounds in the opposite direction at 3.5 m/s. If the collision with the wall endures for a total time of 0.0080 s, then determine the average force acting upon the ball. PSYW

Momentum and Impulse Connection (14 seconds)

33. A 16.0-kg ball is thrown with a speed of 22.0 m/s to a 55-kg clown who is at rest on ice. The clown catches the ball and glides across the ice. Determine the velocity of the clown (and ball) immediately following the catch. PSYW

Using Equations as a "Recipe" for Algebraic Problem-Solving (12 seconds)

34. A 16.0-kg ball is thrown with a speed of 22.0 m/s to a 55-kg clown on ice. At the time that the clown catches the ball, she is moving with a speed of 3.0 m/s in the same direction as the ball. The clown catches the ball and continues to glide across the ice. Determine the velocity of the clown (and ball) immediately following the catch. PSYW

Using Equations as a "Recipe" for Algebraic Problem-Solving (12 seconds)

35. A 0.050-kg billiard ball moving at 1.2 m/s strikes a second 0.050-kg billiard ball which is moving in the same direction with a speed of 0.40 m/s. If the faster ball slows down to a speed of 0.65 m/s, then what is the speed of the second ball? PSYW

Using Equations as a "Recipe" for Algebraic Problem-Solving (12 seconds)

36. A 0.050-kg billiard ball moving at 1.5 m/s strikes a second 0.050-kg billiard ball which is at rest on the table. If the first ball slows down to a speed of 0.10 m/s, then what is the speed of the second ball? PSYW

Using Equations as a "Recipe" for Algebraic Problem-Solving (12 seconds)

37. A 70-kg hockey player moving at 5.6 m/s collides head-on with an 80-kg player who is heading in the opposite direction with a speed of 3.5 m/s. The two players entangle and move together across the ice. Determine their after-collision speed. PSYW

Using Equations as a "Recipe" for Algebraic Problem-Solving (12 seconds)