6: Chapter Energy and Oscillations 1. Which of the following is not an energy unit? A. Nm B. Joule C. calorie D. watt E. kWh Answer: D 2. Work is not being done on an object unless the A. net force on the object is zero. B. object is being accelerated. C. speed is constant. D. object is moving. Answer: D 3. A brick slides across a horizontal rough surface and eventually comes to a stop. What happened to the kinetic energy of the brick? A. Nothing, it is still in the brick but is now called potential energy. B. It was converted to other energy forms, mostly heat. C. It was converted to a potential energy of friction. D. It was simply destroyed in the process of stopping. Answer: B 4. Which of the following is possessed by moving object, but not by a stationary object? A. Energy. B. Kinetic energy. C. Mass. D. Inertia. Answer: B 5. The power of an engine is a measure of A. its volume. B. its ability to outperform a horse. C. the rate at which it can perform work. D. the total amount of work it can perform. Answer: C 6. Which has the greater kinetic energy - a 1-ton car moving at 30 m/s, or a half-ton car moving at 60 m/s? A. a 1-ton car B. a half-ton car C. both have same kinetic energy Answer: B
7. A 20 N ball and a 40 N ball are dropped at the same time from a height of 10 meters. Air resistance is negligible. Which of the following statements is accurate? A. After 1 second has elapsed, both balls have the same kinetic energy since they have the same acceleration. B. The heavy ball has a greater acceleration and falls faster. C. The light ball has a greater speed since it can accelerate faster than the heavy ball. D. Both balls hit the ground at the same time but gravity does more work on the heavy ball than on the light ball. Answer: D 8. When work is done by a force on an object, then which of the following are true? A. The speed of the object always increases. B. The mass of the object always increases. C. The object does negative work on the force. D. The energy lost to friction is equal to the amount of work done by the force. E. The work done will be equal to the change of the total energy of the object plus energy appearing as heat, light, or sound. Answer: E 9. A block sits on a slight incline, held at rest by the frictional force between the block and the incline. Which of the following statements is true? A. The frictional force performs no work since there is no motion of the block. B. The work by the frictional force is equal to the gravitational potential energy of the block. C. The work done by the frictional force is negative since the force of friction opposes the direction that the block is being tugged by gravity. D. The work done by gravity is entirely converted into heat because of the friction present. E. None of these are true. Answer: A 10. A wooden block slides down a rough incline. Which of the following statements is true? A. The kinetic energy of the block is decreasing. B. The gravitational potential energy of the block is increasing. C. The mechanical energy of the block is constant. D. The mechanical energy of the block is increasing. E. The mechanical energy of the block is decreasing. Answer: E
11. Initially, a blue automobile has twice the kinetic energy that a red automobile has. Both are braked to a stop; both have the same amount of braking force. The red auto will stop in ____________________ as the blue auto. A. half the distance B. the same distance C. twice the distance D. four times the distance E. one fourth the distance Answer: D 12. A mass hangs from a spring that is fixed to the ceiling. The mass is now pulled down and released so the mass oscillates up and down. Which of the following statements is true? A. The kinetic energy of the oscillating mass is a constant. B. Adding mass to the spring will make it oscillate faster. C. The restoring force of the spring is equal to the weight of the mass. D. The gravitational force on the mass oscillates at the same frequency as the mass. E. None of the above is true. Answer: E 13. Jim exerts a force of 500 N against a 100-kg desk that does not move. Virgil exerts a force of 400 N against a 60-kg desk that moves 2 m in the direction of the push. Mik exerts a force of 200 N against a 50-kg desk that moves 4 m in the direction of the push. The most work is done by A. Jim. B. Virgil. C. Mik. D. Virgil and Mik, who do equal amounts of work. Answer: D 14. Suppose you climb the stairs of a ten-story building, about 30 m high, and your mass is 60 kg. The gravitational potential energy you gain is about A. 270 Joule. B. 1800 Joule. C. 18000 Joule. D. 27000 Joule. Answer: C
15. Virgil rides a skateboard (combined mass 100 kg) at 4 m/s, and Jill rides a bicycle (combined mass 64 kg) at 5 m/s. A. Virgil has the greater kinetic energy. B. Virgil and Jill have equal kinetic energies. C. Jill has the greater kinetic energy. Answer: B 16. An object with a kinetic energy of 50 J is stopped in a distance of 0.01 m. The average force that stops the object is A. 0.5 N. B. 50 N. C. 500 N. D. 5,000 N. E. 50,000 N. Answer: D 17. A quarterback of mass 85 kg is running at 10 m/s. Also, a tackle of mass 100 kg is running at 9 m/s. A. The quarterback has the greater kinetic energy. B. The quarterback and the tackle have equal kinetic energies. C. The tackle has the greater kinetic energy. Answer: A 18. For a 0.1-kg frog to jump to a height of 1.0 meter requires an energy of about A. 0.1 Joule. B. 0.5 Joule. C. 1.0 Joule. D. 10 Joule. Answer: C 19. A 5.0-kg cat runs to the left at 10 m/s and a 10-kg dog runs to the right at 5.0 m/s. The total kinetic energy is A. -125 Joule. B. 0 C. 100 Joule. D. 375 Joule. E. 500 Joule. Answer: D
20. A child riding on a swing rises to a height 1.0 m above the lowest point. Another child of equal mass whose speed at the lowest point is twice as great will rise A. to the same height. B. twice as high. C. four times as high. D. to a height which depends on the mass. Answer: C 21. A box is moved 10 m across by a floor a force of 20 N acting along the direction of motion. The work done by the force is A. 2.0 J. B. 20 J. C. 30 J. D. 100 J. E. 200 J. Answer: E 22. A box is moved 10 m across a smooth floor by a force making a downward angle with the floor, so that there is effectively a 10 N force acting parallel to the floor in the direction of motion and a 5 N force acting perpendicular to the floor. The work done is A. J. 150 B. 100 J. C. 50 J. D. 10 J. E. 5.0 J. Answer: B 23. A box is pushed across a rough horizontal floor by a force acting parallel to the floor in the direction of motion. A force doing negative work on the body is A. gravity. B. friction. C. the applied force. D. normal reaction force of floor upward on body. E. a fictitious force. Answer: B 24. A box is pushed across a rough horizontal floor by a force acting parallel to the floor in the direction of motion. A force doing no work during the motion is A. gravity. B. friction. C. the applied force. Answer: A
25. The kinetic energy of a body is correctly given by which of the following expressions? A. mv. B. 2mv2. C. mv2. D. ()mv2. E. ()mv. Answer: D 26. A refrigerator weighing 1500 N is to be lifted onto a truck bed that is 1.0 m above the ground. When pushed up a slanting ramp 2.0 m in length a force of only 800 N is required to move it at constant velocity. Comparing the work involved in lifting the refrigerator straight up to the work in pushing it along the ramp, there is A. less work required when the ramp is employed. B. more work required when the ramp is employed. C. an equal amount of work is required in each case. Answer: B 27. Which of the following is not a unit of power? A. watt B. kilowatt C. kilowatt-hour D. joule/second E. horsepower Answer: C 28. If the speed of a car is doubled, the work to stop the car changes by a factor of A. 4. B. 2. C. 1. D. . E. . Answer: A 29. A painter of mass 80 kg climbs 3.0 m up a ladder. The painter's potential energy has increased by A. 240 J. B. 261 J. C. 784 J. D. 1284 J. E. 2352 J. Answer: E
30. The potential energy of a spring of constant k that has been stretched a distance x is given by A. kx. B. ()kx. C. kx2. D. ()kx2. E. ()k/x. Answer: D 31. A pendulum swings through 10 cycles in 5 seconds. The frequency of the pendulum is A. 10 Hz. B. 5 Hz. C. 2 Hz. D. 0.5 Hz. E. 0.1 Hz. Answer: C 32. A grandfather clock that is regulated by a pendulum is taken to the Moon where the acceleration of gravity is less. Compared to an identical clock on Earth, the grandfather clock on the Moon will A. run slow. B. keep time at the same rate. C. run fast. Answer: A 33. A mass hangs on a spring held in physicist's hand. When the mass is pulled down and then released, it oscillates with a period of 2.0 s. This system is taken to the Moon where the acceleration of gravity is less. The spring on the Moon is held in astronaut's hand, and the mass, when pulled down and released, will A. oscillate with a longer period. B. oscillate with unchanged period. C. oscillate with a shorter period. D. will not oscillate at all. Answer: B 34. A grandfather clock that is regulated by a pendulum is orbiting the Earth aboard the space station. Compared to an identical clock on Earth, the grandfather clock aboard the space station will A. run slow. B. keep time at the same rate. C. run fast. D. will not run at all. Answer: D
35. A mass hangs on a spring held in physicist's hand. When the mass is pulled down and then released, it oscillates with a period of 2.0 s. This system is taken to the space station orbiting the Earth. The spring is held in astronaut's hand, and the mass, when pulled down and released, will A. oscillate with a longer period. B. oscillate with unchanged period. C. oscillate with a shorter period. D. will not oscillate at all. Answer: B 36. In order for a body to exhibit simple harmonic motion there must be A. a constant force pushing the body away from the center. B. a constant force drawing the body toward the center. C. a force drawing the body toward the center and increasing with distance away from the center. D. a force pushing the body away from the center and increasing with distance away from the center. E. a force drawing the body toward the center and decreasing with distance away from the center. Answer: C 37. A ball at the end of a string is swinging as a simple pendulum. Assuming no loss in energy due to friction, we can say for the ball that A. the potential energy is maximum at the lowest position of the ball. B. the potential energy is maximum where the kinetic energy is a minimum. C. the potential energy is maximum where the kinetic energy is maximum. D. the kinetic energy is maximum at each end of the motion. Answer: B 38. A body is suspended from a spring hanging vertically. The body is then pulled downward so the spring stretches. Consider the change in the elastic potential energy (EPE) of the spring and the change in gravitational potential energy (GPE) as the body is pulled down. A. The EPE increases but the GPE is unchanged. B. The GPE increases along with the EPE. C. The GPE decreases while the EPE increases. D. The GPE decreases but the EPE is unchanged. E. Both the GPE and the EPE decrease. Answer: C
39. A bullet of mass 0.010 kg and speed of 100 m/s is brought to rest in a wooden block after penetrating a distance of 0.10 m. The work done on the bullet by the block is A. 50 J. B. -50 J. C. 0.001 J. D. -0.001 J. E. zero Answer: B 40. A spring wound clock makes use of elastic____________ energy to drive the mechanism. Answer: potential 41. A force acts on a block moving across a smooth horizontal surface. The work done by this force results in a change of the ___________ energy of the block. Answer: kinetic 42. A ball of mass 5 kg attached to a string is swung in a horizontal circle of radius 1.0 m. If the tension in the string is 10 N the work done by the tension in one revolution is _____________ J. Answer: zero 43. Total mechanical energy of a system is conserved when there are no___________________ forces doing work on the system. Answer: non-conservative or frictional 44. The conversion of the initial potential energy of a person on a sled on a smooth icy slope into kinetic energy at the bottom is an example of the principle of conservation of _________________. Answer: energy or total mechanical energy 45. In pole-vaulting, in addition to gravitational potential energy there is potential energy in the bent pole which is analogous to potential energy stored in a _______________ under compression. Answer: spring 46. Other things being equal, the pole-vaulter having the greatest __________ energy prior to going into the jump should jump the highest. Answer: kinetic 47. A motor rated at 500 watts output is capable of performing _________________ joules of work in 10 seconds. Answer: 5000