Physics: Momentum, Work, Energy, Power

Transcription

1 Name: ate: 1. The momentum of a 5-kilogram object moving at 6 meters per second is. 1 kg m/sec. 5 kg m/sec. 11 kg m/sec. 30 kg m/sec kilogram student running at 3.0 meters per second has a kinetic energy of. 180 J. 270 J. 540 J J 3. cart of mass m traveling at speed v has kinetic energy KE. If the mass of the cart is doubled and its speed is halved, the kinetic energy of the cart will be. half as great. twice as great. one-fourth as great. four times as great 4. Which of the following objects has the greatest momentum?. a 1-kg object moving at 200 m/sec. a 10-kg object moving at 30 m/sec. a 20-kg object moving at 20 m/sec. a 100-kg object moving at 2 m/sec 7. s the unbalanced force applied to an object increases, the time rate of change of the object s momentum. decreases. increases. remains the same 8. cart weighing 10 newtons is pushed 10 meters on a level surface by a force of 5 newtons. What is the increase in its potential energy?. 1 joule. 50 joules. 100 joules. 0 joules 9. n unbalanced 6.0-newton force acts eastward on an object for 3.0 seconds. The impulse produced by the force is. 18 N s east. 2.0 N s east. 18 N s west. 2.0 N s west 10. What is the magnitude of the velocity of a 25-kilogram mass that is moving with a momentum of 100 kilogram-meters per second? m/s m/s. 40 m/s. 4.0 m/s 5. One joule is equivalent to one. newton meter 3. kilogram meter 3. watt 2 newton. kilogram meter 2 second 2 6. s a 1.0-kilogram mass falls freely to the Earth, its momentum kilogram mass travels east with a constant velocity of 40 meters per second. The momentum of this mass is kg m/s east kg m/s east kg m/s west kg m/s west. decreases. increases. remains the same page 1

2 kilogram bullet is fired from a rifle by an unbalanced force of 200 newtons. If the force acts on the bullet for 0.1 second, what is the maximum speed attained by the bullet?. 5 m/s. 20 m/s 17. Each of the blocks in the diagrams is lifted vertically for the distance indicated. Which block will gain the most gravitational potential energy? m/s. 800 m/s 13. pendulum swings as shown in the diagram. t which position is the kinetic energy of the pendulum bob least? constant braking force of 10 newtons applied for 5 seconds is used to stop a 2.5-kilogram cart traveling at 20 meters per second. The magnitude of the impulse applied to stop the cart is. 10 N s. 30 N s.. 50 N s. 100 N s 15. Two rocks weighing 5 newtons and 10 newtons, respectively, fall freely from rest near the Earth s surface. fter 3 seconds of free-fall, compared to the 5-newton rock, the 10-newton rock has greater. acceleration. height. momentum. speed 16. In a baseball game, a batter hits a ball for a home run. ompared to the magnitude of the impulse imparted to the ball, the magnitude of the impulse imparted to the bat is 18. student drops two eggs of equal mass simultaneously from the same height. Egg lands on the tile floor and breaks. Egg lands intact without bouncing, on a foam pad lying on the floor. ompared to the magnitude of the impulse on egg as it lands, the magnitude of the impulse on egg as it lands is. less. greater. the same. less. greater. the same 19. n object 10 meters above the ground has Z joules of potential energy. If the object falls freely, how many joules of kinetic energy will it have gained when it is 5 meters above the ground?. Z. 2Z. Z 2. 0 page 2

3 kilogram softball initially at rest is hit with a bat. The ball is in contact with the bat for 0.20 second and leaves the bat with a speed of 25 meters per second. What is the magnitude of the average force exerted by the ball on the bat? 24. In the diagram below, a 60.-kilogram rollerskater exerts a 10.-newton force on a 30.-kilogram rollerskater for 0.20 second N. 15 N. 3.0 N. 75 N 21. If the speed of a moving object is doubled, which quantity associated with the object must also double?. its momentum. its kinetic energy. its acceleration. its gravitational potential energy 22. The magnitude of the momentum of an object is 64.0 kilogram meters per second. If the velocity of the object is doubled, the magnitude of the momentum of the object will be kg m/s kg m/s. 128 kg m/s. 256 kg m/s 23. Which is an acceptable unit for impulse?. N m. J/s. J s. kg m/s What is the magnitude of the impulse applied to the 30.-kilogram rollerskater?. 50. N s. 2.0 N s. 6.0 N s. 12 N s 25. Which two quantities can be expressed using the same units?. energy and force. impulse and force. momentum and energy. impulse and momentum 26. Four machines do the amounts of work listed in the table shown. The time they take to do the work is also listed. Which machine develops the most power? Machine Work Time 1,000 joules 5 sec 1,000 joules 10 sec 2,000 joules 5 sec 2,000 joules 10 sec.... page 3

4 27. How much work is required to lift a 2-kilogram mass to a height of 10 meters?. 5 joules. 20 joules. 100 joules. 200 joules 28. garden tractor drags a plow with a force of 500 newtons a distance of 10 meters in 20 seconds. How much work is done?. 25 joules. 1,000 joules. 2,500 joules. 5,000 joules 29. s the length of time it takes a student to swim 100 meters decreases, the power developed by the student. decreases. increases. remains the same 30. How much work will a 500-watt motor do in 10 seconds? joule. 50 joules. 500 joules. 5,000 joules 32. What force is required to do 60 joules of work in sliding an object a distance of 10 meters across a level floor?. 6 newtons. 10 newtons. 60 newtons. 600 newtons 33. ar and car are of equal mass and travel up a hill. ar moves up the hill at a constant speed that is twice the constant speed of car. ompared to the power developed by car, the power developed by car is. the same. twice as much. half as much. four times as much 34. What is the maximum distance that a 60-watt motor may vertically lift a 90-newton weight in 7.5 seconds?. 2.3 m. 5.0 m. 140 m m 35. The graph shows the force exerted on a block as a function of the block s displacement in the direction of the force. How much work did the force do in displacing the block 5.0 meters? 31. The diagram here shows a 1-kilogram aluminum sphere and a 3-kilogram copper sphere of equal radius located 20 meters above the ground.. 0 J. 20 J J. 4.0 J Just before striking the ground, the speed of the copper sphere is 20 meters per second. What is the momentum of the copper sphere?. 10 kg-m/sec. 20 kg-m/sec 36. If a net force of 10 newtons acts on a 6.0-kilogram mass for 8.0 seconds, the total change of momentum of the mass is. 48 kg m/s. 60 kg m/s. 80 kg m/s. 480 kg m/s. 60 kg-m/sec. 600 kg-m/sec page 4

5 37. The diagram shows a newton crate to be lifted at constant speed from the ground to a loading dock 1.5 meters high in 5.0 seconds. What power is required to lift the crate? 40. force is applied to a block, causing it to accelerate along a horizontal, frictionless surface. The energy gained by the block is equal to the. work done on the block. power applied to the block. impulse applied to the block W W W W 38. box is pushed to the right with a varying horizontal force. The graph below represents the relationship between the applied force and the distance the box moves.. momentum given to the block kilogram boy initially at rest skis down the slope as shown. ssuming no frictional loss, what will be his kinetic energy at the bottom of the slope? Force vs.istance. 1,500 joules. 7,500 joules. 15,000 joules. 75,000 joules 42. s a falling apple approaches the ground, its potential energy What is the total work done in moving the box 6.0 meters?. 9.0 J. 18 J. 27 J. 36 J kilogram person acquires a velocity of 15 meters per second down a ski slope. What is the skier s kinetic energy?. 22,500 joules. 11,250 joules. 1,500 joules. 115 joules. decreases. increases. remains the same 43. The work done in raising an object must result in an increase in the object s. internal energy. kinetic energy. gravitational potential energy. heat energy page 5

6 44. s the pendulum swings from position to position as shown in the diagram, what is the relationship of kinetic energy to potential energy? [Neglect friction.] 48. Work is being done when a force. acts vertically on a cart that can only move horizontally. is exerted by one team in a tug of war when there is no movement. is exerted while pulling a wagon up a hill. The kinetic energy decrease is more than the potential energy increase.. The kinetic energy increase is more than the potential energy decrease.. The kinetic energy decrease is equal to the potential energy increase.. The kinetic energy increase is equal to the potential energy decrease. 45. How long would it take a machine to do 5,000 joules of work if the power rating of the machine is 100 watts?. 5,000 sec. 50 sec. of gravitational attraction acts on a person standing on the surface of the Earth 49. The Earth is closest to the Sun during January and farthest from the Sun during July. uring which month is the gravitational potential energy of the Earth with respect to the Sun the greatest?. January. March. July. September 50. Three people of equal mass climb a mountain using paths,, and shown in the diagram. long which path(s) does a person gain the greatest amount of gravitational potential energy from start to finish?. 10 sec. 0.2 sec 46. basketball player who weighs 600 newtons jumps 0.5 meter vertically off the floor. What is her kinetic energy just before hitting the floor?. 30 J. 60 J. 300 J. 600 J 47. If the speed of an object is doubled, its kinetic energy will be. halved. doubled., only., only., only. The gain is the same along all paths.. quartered. quadrupled page 6

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