Review the following concepts if needed:

- Momentum Help
- Physics and Collisions Help
- Physics and Work Help
- Physics and Energy Help
- Physics and Power Help

**Momentum, Work, Energy, And Power Practice Test**

A good score is eight correct. Answers are given at the end.

1. Consider a minor parking-lot accident. Car *A* backs out at 30 cm/s toward the west, and car *B* looks for a place to park, driving north at 40 cm/s. Both cars mass 1,000 kg. What is the total system momentum before the collision? Remember that momentum is a vector quantity. Also, be careful with your units.

(a) 700 kg · m/s, generally northwest

(b) 100 kg · m/s, generally northwest

(c) 500 kg · m/s, generally northwest

(d) There is not enough information to answer this.

2. Impulse is the product of

(a) time and distance.

(b) time, mass, and acceleration.

(c) time, mass, and velocity.

(d) time and velocity.

3. Consider a hockey player skating down the ice at 10.0 m/s. His mass is 82.0 kg. What is his kinetic energy?

(a) 820 J

(b) 410 J

(c) 8.20 × 10 ^{4} J

(d) 4.10 × 10 ^{3} J

4. An object whose mass is 10.0 kg is lifted through a distance of 4.000 m on a planet where the gravitational acceleration is 6.000 m/s ^{2} . How much work is required to do this?

(a) 60.0 J

(b) 24.0 J

(c) 40.0 J

(d) 240 J

5. Suppose that an object is pushed with steady force along a frictionless surface. When you multiply the object’s mass by the length of time for which it is pushed and then multiply the result by the object’s acceleration over that period of time, you get

(a) momentum.

(b) velocity.

(c) impulse.

(d) a meaningless quantity.

6. According to the law of conservation of momentum, in an ideal closed system,

(a) when two objects collide, the system neither loses nor gains any total momentum.

(b) when two objects collide, neither object loses or gains any momentum.

(c) when two objects collide, the magnitudes of their momentum vectors add.

(d) when two objects collide, the magnitudes of their momentum vectors multiply.

7. When making calculations in which all the quantities have their units indicated throughout the entire process,

(a) the units multiply and divide just like the numbers.

(b) the units cannot cancel out.

(c) the units can be multiplied but not divided.

(d) the units can be added and subtracted, but not multiplied or divided.

8. One joule, reduced to base units, is equivalent to

(a) one kilogram-meter per second squared.

(b) one kilogram-meter.

(c) one kilogram-meter squared per second squared.

(d) one meter per second squared.

9. A 5,000-kg motorboat sits still on a frictionless lake. There is no wind to push against the boat. The captain starts the motor and runs it steadily for 10.00 seconds in a direction straight forward and then shuts the motor down. The boat has attained a speed of 5.000 meters per second straight forward. What is the impulse supplied by the motor?

(a) 2.500 × 10 ^{5} kg · m/s

(b) 2.500 × 10 ^{4} kg · m/s

(c) 2,500 kg · m/s

(d) 6.250 × 10 ^{4} kg · m/s

10. Which of the following does *not* have an effect on the momentum of a moving spherical particle?

(a) The speed of the particle

(b) The diameter of the particle

(c) The direction in which the particle travels

(d) The mass of the particle

**Answers **

1. c

2. b

3. d

4. d

5. c

6. a

7. a

8. c

9. b

10. b

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