PHY 102 (Atoms to Galaxies), HW4, Bergfield (ISU)2021/2022

The SI units of work are A. Calories B. Kilocalories C. Joules D. Watts E. Newtons Answer- C. Joules An elevator lifts a person from the 1st floor to the 4th floor in 30s. If the power output of the elevator is 5800W, what is the work done by the elevator? A. 174,000 J B. 12,431 J C. 58,000 J D. 58 J E. none of these Answer- A. 174,000 J A 75 kg man climbs the stairs to the fifth floor of a building, a total height of 16 m. His potential energy has increased by approximately A. 12000 J B. 59000 J C. 47000 J D. 38000 J E. 5900 J Answer- A. 12000 J A ball rolling down an incline has its maximum kinetic energy at A. the top. B. a quarter of the way down. C. halfway down. D. three-quarters of the way down. E. the bottom. Answer- E. the bottom. The power required to exert 64N of force over a distance of 8m in 32 seconds is A. 128 W B. 32,000 W C. 16 W D. 96 W E. impossible to predict Answer- C. 16 W A diver who weighs 500 N steps off a diving board that is 10 m above the water. The diver hits the water with kinetic energy of A. 10 J. B. 500 J. C. 510 J. D. 5000 J. E. more than 5000 J. Answer- D. 5000 J. A light aluminum ball and a heavy lead ball of the same size are allowed to roll down an incline. When they are halfway down the incline, they will have identical A. kinetic energies. B. potential energies. C. momentum. D. inertia. E. none of the above choices Answer- E. none of the above choices A person drops one rock from rest and it falls 100 meters down a cliff before hitting the ground. The person then throws an identical rock downward. The amount of kinetic energy gained by the rock dropped from rest is ________ that of the second rock, and the change in potential energy of the rock dropped from rest is _________ that of the second rock. A. equal to, greater than B. equal to, equal to C. less than, less than D. equal to, less than E. less than, equal to Answer- B. equal to, equal to A skydiver falls through the air gaining 20 J of kinetic energy. How much gravitational potential energy did she lose? Include air resistance. A. 20 J B. more than 20 J C. less than 20 J D. One needs to know the mass of the skydiver. E. One needs to know how far she fell. Answer- B. more than 20 J A wind turbine converts _______________ energy into electrical energy. A. chemical B. gravitational C. mechanical D. thermal E. nuclear Answer- C. mechanical A woman runs up a flight of stairs. The gain in her gravitational potential energy is 100 J. If she runs up the same stairs with twice the speed, what is her gain in potential energy? A. 100 J B. 200 J C. 50 J D. 400 J E. 25 J Answer- A. 100 J After rolling halfway down an incline after being released from rest, a marble's kinetic energy is A. less than its potential energy. B. greater than its potential energy. C. the same as its potential energy. D. impossible to determine. E. zero. Answer- C. the same as its potential energy. An object lifted 10 meters gains 200 J of potential energy. If the same object is lifted 20 meters, its potential energy gain is A. half as much. B. the same. C. twice as much. D. four times as much. E. more than four times as much. Answer- C. twice as much. If an object is raised twice as high, its potential energy will be A. half as much B. twice as much. C. four times as much. D. impossible to determine unless the time is given. E. impossible to determine unless the mass is given. Answer- B. twice as much. Susan ascends a mountain via a short, steep trail. Sean ascends the same mountain via a long, gentle trail. Which of the following statements is true? A. Susan gains more gravitational potential energy than Sean. B. Susan gains less gravitational potential energy that Sean. C. Susan gains the same gravitational potential energy as Sean. D. To compare gravitational potential energies, we must know the height of the mountain. E. To compare gravitational potential energies, we must know the length of the two trails. Answer- C. Susan gains the same gravitational potential energy as Sean. The SI units of energy are A. Calories B. Kilocalories C. Joules D. Watts E. Newtons Answer- C. Joules The ball rolling down an incline has its maximum potential energy at A. the top. B. a quarter of the way down. C. halfway down. D. three-quarters of the way down. E. the bottom. Answer- A. the top. The energy stored in one pound of fat is about A. 35 Cal B. 350 Cal C. 1000 Cal D. 3500 Cal E. 5000 Cal Answer- D. 3500 Cal True or False: A 15 kg crate sliding at 4.0 m/s comes to rest due to friction. The amount of thermal energy generated by this process is 60 J. A. True B. False Answer- B. False True or False: Gravitational potential energy depends on the object's mass. A. True B. False Answer- A. True