(DO NOT WRITE ON THIS TEST)

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1 Phy Final Prep Chap 8 (DO NOT WRITE ON THIS TEST) Multiple Choice Identify the choice that best completes the statement or answers the question. 1. If Nellie Newton pushes an object with twice the force for twice the distance, she does a. twice the work. b. the same work. c. four times the work. d. eight times the work. 2. The unit of work is the a. watt. b. meter. c. joule. d. newton. e. second. 3. Power is defined as the a. force on an object divided by the time the force acts. b. work done times the time taken to do that work. c. work done on an object divided by the time taken to do the work. d. distance divided by the time taken to move that distance. e. force on an object times the distance the object moves. 4. How much farther will a car traveling at 100 km/s skid than the same car traveling at 50 km/s? a. Half as far. b. The same distance. c. Twice as far. d. Four times as far. e. Five times as far. 5. An arrow in a bow has 70 J of potential energy. Assuming no loss of energy to heat, how much kinetic energy will it have after it has been shot? a. 0 J b. 35 J c. 50 J d. 70 J e. 140 J 6. As a pendulum swings back and forth a. at the end points of its swing, its energy is all potential. b. at the lowest part of its swing, its energy is all kinetic. c. kinetic energy is transformed into potential energy. d. potential energy is transformed into kinetic energy. e. all of the above 7. Rockets are launched from an airplane in the forward direction of motion. The kinetic energy of the airplane will be a. unchanged. b. increased. c. decreased.

2 8. A woman can lift barrels a vertical distance of 1 meter or can roll them up a 2-meter long ramp to the same elevation. If she uses the ramp, the applied force required is a. 1 4 b. 1 2 as much. as much. c. the same amount. d. 2 times as much. e. 4 times as much. 9. An object that has kinetic energy must be a. at rest. b. falling. c. moving. d. elevated. 10. A heavy object and a light object are released from rest at the same height and time in a vacuum. As they fall, they have equal a. energies. b. weights. c. momenta. d. all of the above 11. If an object has kinetic energy, then it also must have a. impulse. b. force. c. momentum. d. acceleration. 12. If the velocity of a moving object doubles, then what else doubles? a. acceleration. b. kinetic energy. c. momentum. d. all of the above 13. A small economy car (low mass) and a limousine (high mass) are pushed from rest across a parking lot, equal distances with equal forces. The car that receives more kinetic energy is the a. the limousine. b. the small economy car. c. neither one they receive the same amount of kinetic energy. 14. How many joules of work are done on a box when a force of 25 N pushes it 3 m? a. 1 J b. 3 J c. 8 J d. 25 J e. 75 J

3 15. How much work is done on a 20-N crate that you lift 2 m? a. 0 J b. 1 J c. 2 J d. 20 J e. 40 J 16. How much power is expended if you lift a 60 N crate 10 meters in 1 second? a. 0 W b. 6 W c. 10 W d. 60 W e. 600 W 17. It takes 80 J to push a large box 8 m across a floor. Assuming the push is in the same direction as the move, what is the magnitude of the force on the box? a. 8 N b. 10 N c. 80 N d. 640 N 18. A 60-N object moves at 1 m/s. Its kinetic energy is a. 1 J. b. 3 J. c. 60 J. d. more than 60 J. 19. Sue can easily lift a 45.0-N rock with the help of a lever. When she pushes down with 20.0 N of force, she lifts the rock 0.3 meters. How far does she move her arms to do this? a. 0.3 m b. 0.7 m c. 6.0 m d. 2.3 m e m 20. A certain jack has a theoretical mechanical advantage of 300. However, due to frictional forces, the actual mechanical advantage is only 100. What is the efficiency of the jack? a. 1 3 b. 3 c. 30 d. 300 e. 30,000

4 True/False Indicate whether the statement is true or false. 21. The rate at which work is done is called energy. 22. The unit of power is the watt. 23. When we carry an object across a room, without lifting it or setting it down, we do no physical work on it. 24. In a grandfather clock, mechanical energy enables a pendulum to swing back and forth. 25. Fossil fuels are both plentiful and inexpensive. Problem (Show your work) 26. What is the work done in lifting 60 kg of blocks to a height of 20 m? 27. A toy cart moves with a kinetic energy of 10 J. If its speed is doubled, what will its kinetic energy be? 28. A 30-kg girl runs up the staircase to a floor 5 m higher in 8 seconds. What is her power output? 29. At what height does a 1000-kg mass have a potential energy of 1 J relative to the ground? 30. The 4.0-kg head of an ax is moving at 4.0 m/s when it strikes a log and penetrates 0.01 m into the log. What is the average force the blade exerts on the log? 31. An anvil hanging vertically from a long rope in a barn is pulled to the side and raised like a pendulum 1.60 m above its equilibrium position. It then swings to its lowermost point where the rope is cut by a sharp blade. The anvil then has a horizontal velocity with which it sails across the barn and hits the floor, 10.0 m below. How far horizontally along the floor will the anvil land?

5 Phy Final Prep Chap 8 Answer Section MULTIPLE CHOICE 1. ANS: C PTS: 1 DIF: L2 OBJ: 9.1 Work STA: Ph.3.a KEY: force distance BLM: comprehension 2. ANS: C PTS: 1 DIF: L1 OBJ: 9.1 Work STA: Ph.3.a KEY: work joule BLM: knowledge 3. ANS: C PTS: 1 DIF: L1 OBJ: 9.2 Power KEY: power work time BLM: knowledge 4. ANS: D PTS: 1 DIF: L2 OBJ: 9.5 Kinetic Energy STA: Ph.2.a KEY: energy speed BLM: comprehension 5. ANS: D PTS: 1 DIF: L2 OBJ: 9.6 Work-Energy Theorem STA: Ph.2.c KEY: potential energy kinetic BLM: comprehension 6. ANS: E PTS: 1 DIF: L2 OBJ: 9.6 Work-Energy Theorem STA: Ph.2.c KEY: pendulum potential kinetic BLM: comprehension 7. ANS: C PTS: 1 DIF: L2 OBJ: 9.5 Kinetic Energy STA: Ph.2.a KEY: kinetic motion BLM: comprehension 8. ANS: B PTS: 1 DIF: L2 OBJ: 9.8 Machines KEY: force ramp BLM: application 9. ANS: C PTS: 1 DIF: L1 OBJ: 9.5 Kinetic Energy STA: Ph.2.a KEY: kinetic energy BLM: knowledge 10. ANS: E PTS: 1 DIF: L2 OBJ: 9.3 Mechanical Energy KEY: vacuum fall weight BLM: comprehension 11. ANS: C PTS: 1 DIF: L2 OBJ: 9.5 Kinetic Energy STA: Ph.2.a KEY: kinetic momentum BLM: comprehension 12. ANS: C PTS: 1 DIF: L2 OBJ: 9.5 Kinetic Energy STA: Ph.2.a KEY: velocity momentum BLM: comprehension 13. ANS: C PTS: 1 DIF: L2 OBJ: 9.5 Kinetic Energy STA: Ph.2.a KEY: kinetic energy BLM: comprehension 14. ANS: E PTS: 1 DIF: L2 OBJ: 9.1 Work STA: Ph.3.a KEY: joule work force BLM: application 15. ANS: E PTS: 1 DIF: L2 OBJ: 9.1 Work STA: Ph.3.a KEY: lift work distance BLM: application 16. ANS: E PTS: 1 DIF: L2 OBJ: 9.2 Power KEY: power time BLM: application 17. ANS: B PTS: 1 DIF: L2 OBJ: 9.1 Work STA: Ph.3.a KEY: force joule magnitude BLM: application 18. ANS: B PTS: 1 DIF: L2 OBJ: 9.5 Kinetic Energy STA: Ph.2.a KEY: kinetic energy BLM: application 19. ANS: B PTS: 1 DIF: L2 OBJ: 9.7 Conservation of Energy KEY: lever force distance BLM: application 20. ANS: A PTS: 1 DIF: L2 OBJ: 9.8 Machines KEY: mechanical advantage actual BLM: application

6 TRUE/FALSE 21. ANS: F PTS: 1 DIF: L1 OBJ: 9.2 Power KEY: work energy rate BLM: knowledge 22. ANS: T PTS: 1 DIF: L1 OBJ: 9.2 Power KEY: power watt BLM: knowledge 23. ANS: T PTS: 1 DIF: L2 OBJ: 9.1 Work STA: Ph.3.a KEY: work BLM: comprehension 24. ANS: T PTS: 1 DIF: L1 OBJ: 9.3 Mechanical Energy KEY: mechanical energy BLM: application 25. ANS: F PTS: 1 DIF: L2 OBJ: 9.10 Energy for Life KEY: energy conservation BLM: comprehension PROBLEM 26. ANS: 12,000 J PTS: 1 DIF: L2 OBJ: 9.1 Work STA: Ph.3.a KEY: work BLM: application 27. ANS: 40 J PTS: 1 DIF: L2 OBJ: 9.5 Kinetic Energy STA: Ph.2.a KEY: kinetic energy speed BLM: application 28. ANS: 188 W PTS: 1 DIF: L2 OBJ: 9.2 Power KEY: mass power BLM: application 29. ANS: 0.00 m PTS: 1 DIF: L2 OBJ: 9.4 Potential Energy STA: Ph.2.b KEY: mass potential energy BLM: application 30. ANS: 3200 N PTS: 1 DIF: L2 OBJ: 9.5 Kinetic Energy STA: Ph.2.a KEY: force BLM: application 31. ANS: 8.0 m PTS: 1 DIF: L2 OBJ: 9.6 Work-Energy Theorem STA: Ph.2.c KEY: pendulum velocity BLM: application