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Home , Elastic energy, Gravitational energy

Unit VII

Multiple Choice

Identify the choice that best completes the statement or answers the question.

1. Which of the following statements is true according to the law of ? a. Energy cannot be created. b. Energy cannot be destroyed. c. Energy can be transferred from one form to another. d. all of the above

2. An object’s gravitational is NOT directly related to which of the following? a. its height relative to a reference level c. its speed b. its d. the strength

3. Which statement about the slope of the force vs stretch graph is NOT true? a. The slope equals the energy stored in the . b. The slope is equal to the spring constant. c. The slope describes the amount of force needed to stretch the spring one meter d. The slope describes the spring’s resistance to stretch.

4. Determine how much energy is stored by stretching the spring represented in the graph from 0 to 0.10m. a. 0 J b. 5 J c. 10 J d. 20 J

5. Which of the following energy forms is associated with an object in motion? a. c. nonmechanical energy b. elastic potential energy d.

6. How much elastic potential energy is stored in a bungee cord with a spring constant of 10.0 N/m when the cord is stretched 15 m? a. 10.0 J b. 75 J c. 150 J d. 1125 J

7. energy must be measured in relation to a. kinetic energy. c. total potential energy. b. . d. a determined point of zero elevation.

Two balls in the diagam above have equal mass and are released from rest at the heights indicated.

8. How does the gravitational energy of ball B compare to ball A before they are released? a. B has twice as much as A c. B has 4 times as much as A b. B has half as much as A d. They have the same amount

Consider the diagram above which shows two balls, A and B, which are dropped from the same height.

Ball B has twice the mass of ball A. (Mass A = 1 kg and Mass B = 2 kg)

9. How does the gravitational energy of Ball B compare to that of Ball A? a. They are the same c. B has twice as much as A b. B has half as much as A d. B has 4 times as much as A

10. How does the acceleration of B compare to that of A? a. A is greater than B b. B is greater that A c. A is equal to B

11. What is the kinetic energy of a 0.135 kg baseball thrown at 40.0 m/s? a. 54.0 J b. 87.0 J c. 108 J d. 216 J

12. What is the unit of ? a. c. watt b. newton/meter d. all of the above

13. In which of the following sentences is work used in the everyday understanding of the word and not the scientific understanding? a. Lifting a heavy bucket involves doing work on the bucket. b. The force of friction usually does negative work. c. Sam and Rachel worked hard pushing the car but could not move it. d. Work is equal to the change in energy of a system.

14. What is the approximate gravitational potential energy of a 1.0 kg mass 1.0 m above the ground? a. 1.0 J b. 10 J c. 50 J d. 96 J

Figure 15-1

15. The kinetic energy of the pendulum bob in Figure 15-1 increases the most between locations a. A and B. c. B and D. b. A and C. d. C and D.

16. Friction converts kinetic energy to which form? a. gravitational potential energy. c. . b. elastic potential energy. d. total energy.

17. If the sign of work is negative which of the following statements would be true? The displacement of the object is a. perpendicular to the force and no work is done. b. in the direction opposite the force and energy leaves the system. c. in the same direction as the force and energy enters the system. d. in the direction opposite the force and energy enters the system.

18. A horizontal force of 200 N is applied to move a 55 kg television set across a 10 m level surface. What is the work done by the 200 N force on the television set? a. 550 J c. 6,000 J b. 2,000 J d. 11,000 J

19. A 3.00 kg toy falls from a height of 1 m. How much energy is stored as gravitational before the toy falls? a. 1 J c. 30 J b. 10 J d. 300 J

20. Work is a transfer of a. energy. c. mass. b. force. d. motion.

For the following questions consider the diagram representing a portion of an amusement park ride. Before the 100 kg car begins moving it has 30,000 J of Gravitational Potential Energy at point A. It moves down a frictionless track and comes to a stop as it compresses a huge spring at point D.

21. In what order should the energy bar graphs be arranged to explain the motion of the roller coaster car?

a. 1, 4, 2, 3 c. 3, 2, 4, 1 b. 2, 4, 3, 1 d. 2, 4, 1, 3

22. How much gravitational energy does the car have at point B? a. 30,000 J c. 10,000 J b. 20,000 J d. 0 J

23. How fast is the car moving at point C? a. 0 m/s c. 24.5 m/s b. 20 m/s d. 31.6 m/s

24. Which of the following increases when the temperature or particle motion of an object increases? a. b. elastic potential energy c. nuclear energy d. internal energy

25. Which of the following is an example of an object with elastic potential energy? a. a stretched bungee cord b. a compressed spring c. a stretched rubber band d. all of the above

26. It takes 40 J to push a large box 4 m across a floor. Assuming that the push is in the same direction as the displacement, what is the size of the force on the box? a. 4 N b. 10 N c. 40 N d. none of these

27. If you perform 40 of work lifting a 10-N box from the floor to a shelf, how high is the shelf? a. 0.3 m c. 4.0 m b. 20 m d. 400 m

Short Answer

28. You and your lab partner perform an energy experiment. Your job is to take snapshots at points in the experiment. The first picture shows your lab partner standing at the edge of a 10 m high building. The 2nd shows him after he has jumped off and landed on a trampoline stretching it so that he is at ground level and not moving (Intermediate situation). The 3rd shot shows him after the trampoline has launched him into the air; he is 5 m above the ground and still moving. Assume that none of the energy becomes internal (an ideal trampoline).

a. Sketch the energy bars to describe this situation.

b. Is your partner still moving in the final shot? Explain how you know.

29. Suppose the spring below has a spring constant of 50. N/m. The box has a mass of 8.0 kg and rests on a surface of negligible friction (that means it can be ignored).

˜ a. In the diagram at left, the spring was compressed 4.0 m. How much energy does the compressed spring store? Show your work including equation used.

b. Suppose that all the were transferred to the box when it was released. How fast would the box be moving just after release? Show your work including equation used.

c. Explain what happens to the energy as the box slides to a stop?

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Unit VII Energy

Answer Section

MULTIPLE CHOICE

1. ANS: D PTS: 1 DIF: L1 OBJ: 15.2.2

STA: OHPS.9.IN.15

2. ANS: C PTS: 1 DIF: L1 OBJ: 15.1.3

STA: OHPS.9.10.BM.E | OHPS.9.IN.12

3. ANS: A PTS: 1

4. ANS: C PTS: 1

5. ANS: D PTS: 1 DIF: I OBJ: 5-2.1

6. ANS: D

Given

Solution

PTS: 1 DIF: IIIA OBJ: 5-2.6

7. ANS: D PTS: 1 DIF: I OBJ: 5-2.5

8. ANS: A PTS: 1

9. ANS: C PTS: 1

10. ANS: C PTS: 1

11. ANS: C

Given

Solution

PTS: 1 DIF: IIIA OBJ: 5-2.2

12. ANS: A PTS: 1 DIF: L1 OBJ: 14.1.2

13. ANS: C PTS: 1 DIF: I OBJ: 5-1.1

14. ANS: B

Given

Solution

PTS: 1 DIF: IIIA OBJ: 5-2.6

15. ANS: B PTS: 1 DIF: L2 OBJ: 15.2.3

STA: OHPS.9.10.BM.F

16. ANS: C PTS: 1 DIF: I OBJ: 5-3.2

17. ANS: B PTS: 1 DIF: II OBJ: 5-1.2

18. ANS: B

Given

Solution

PTS: 1 DIF: IIIA OBJ: 5-1.4

19. ANS: C

Given

Solution

PTS: 1 DIF: IIIA OBJ: 5-3.3

20. ANS: A PTS: 1 DIF: L1 OBJ: 15.1.1

21. ANS: D PTS: 1

22. ANS: C PTS: 1

23. ANS: D PTS: 1

24. ANS: D PTS: 1 DIF: L1 OBJ: 15.1.5

STA: OHPS.9.IN.13

25. ANS: D PTS: 1 DIF: L1 OBJ: 15.1.3

STA: OHPS.9.10.BM.E | OHPS.9.IN.12

26. ANS: B PTS: 1

27. ANS: C PTS: 1 DIF: L2 OBJ: 14.1.2

SHORT ANSWER

28. ANS:

answer

PTS: 1

29. ANS:

answer

PTS: 1