Work Energy Review. 1. Base your answer to the following question on the information and diagram below and on your knowledge of physics.

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1 Name: ate: 1. ase your answer to the following question on the information and diagram below and on your knowledge of physics. student pushes a box, weighing 50. newtons, 6.0 meters up an incline at a constant speed by applying a force of 25 newtons parallel to the incline. The top of the incline is 2.0 meters higher than the bottom. 2. escribe what would happen to the total work done on the box by the student to push the box 6.0 meters up the incline at constant speed if the coefficient of kinetic friction between the box and the incline were increased. alculate the total work done on the box by the student while pushing the box from the bottom to the top of the incline. [Show all work, including the equation and substitution with units.] 3. (The diagram below represents a 35-newton block hanging from a vertical spring, causing the spring to elongate from its original length. Unstretched spring Stretched spring etermine the spring constant of the spring. page 1

2 4. ase your answer to the following question on the information and diagram below and on your knowledge of physics. s represented in the diagram, a ski area rope-tow pulls a 72.0-kilogram skier from the bottom to the top of a 40.0-meter-high hill. The rope-tow exerts a force of magnitude 158 newtons to move the skier a total distance of 230. meters up the side of the hill at constant speed. etermine the total amount of work done by the rope on the skier. 5. alculate the total amount of gravitational potential energy gained by the skier while moving up the hill. [Show all work, including the equation and substitution with units] 6. escribe what happens to the internal energy of the skier-hill system as the skier is pulled up the hill. 7. escribe what happens to the total mechanical energy of the skier-hill system as the skier is pulled up the hill. 10. Two objects, and, are held one meter above the horizontal ground. The mass of is twice as great as the mass of. If PE is the gravitational potential energy of relative to the ground, then the gravitational potential energy of relative to the ground is. PE. 2PE. PE 2. 4PE 11. What is the kinetic energy of a 55-kilogram skier traveling at 9.0 meters per second? 8. horizontal force of 20 newtons eastward causes a 10-kilogram box to have a displacement of 5 meters eastward. The total work done on the box by the 20-newton force is. 40 J. 100 J. 200 J J 9. block initially at rest on a horizontal, frictionless surface is accelerated by a constant horizontal force of 5.0 newtons. If 15 joules of work is done on the block by this force while accelerating it, the kinetic energy of the block increases by J J J J 12. motor does a total of 480 joules of work in 5.0 seconds to lift a 12-kilogram block to the top of a ramp. The average power developed by the motor is. 8.0 W. 40. W. 96 W W. 3.0 J. 15 J. 20. J. 75 J page 2

3 watt elevator motor can lift a total weight of newtons with a maximum constant speed of m/s m/s. 2.8 m/s. 3.6 m/s page 3

4 ase your answer to the following question on the information and diagram below and on your knowledge of physics. jack-in-the-box is a toy in which a figure in an open box is pushed down, compressing a spring. The lid of the box is then closed. When the box is opened, the figure is pushed up by the spring. The spring in the toy is compressed meter by using a downward force of 12.0 newtons. page 4

5 14. alculate the spring constant of the spring. 15. alculate the total amount of elastic potential energy stored in the spring when it is compressed. 16. Identify one form of energy to which the elastic potential energy of the spring is converted when the figure is pushed up by the spring. 18. Which graph best represents the relationship between the potential energy stored in a spring and the change in the spring s length from its equilibrium position?. 17. block slides across a rough, horizontal tabletop. s the block comes to rest, there is an increase in the block-tabletop system s.. gravitational potential energy. elastic potential energy. kinetic energy. internal (thermal) energy 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 20. 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 page 5

6 21. 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. 10 sec. 0.2 sec 22. ar and car of equal mass 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 23. In the diagram, 55 joules of work is needed to raise a 10-newton weight 5.0 meters. How much work is done to overcome friction as the weight is raised?. 5 J. 5.5 J. 11 J. 50 J newton block is at rest at the bottom of a frictionless incline as shown in the diagram. How much work must be done against gravity to move the block to the top of the incline?. 10 J. 60 J. 80 J. 100 J 26. 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. of gravitational attraction acts on a person standing on the surface of the Earth 27. motor has an output of 1,000 watts. When the motor is working at full capacity, how much time will it require to lift a 50-newton weight 100 meters?. 5 s. 10 s. 50 s. 100 s 28. If the time required for a student to swim 500 meters is doubled, the power developed by the student will be 24. One joule is equivalent to one. newton meter 3. kilogram meter 3. watt 2 newton. kilogram meter 2 second 2. halved. doubled. quatered. quadrupled 29. student applies a 20.-newton force to move a crate at a constant speed of 4.0 meters per second across a rough floor. How much work is done by the student on the crate in 6.0 seconds?. 80. J. 120 J. 240 J. 480 J page 6

7 30. The accompanying graph represents the elongation of a spring as a function of the applied force. 32. The graph below shows the relationship between the work done by a student and the time of ascent as the student runs up a flight of stairs. The slope of the graph would have units of How much work must be done to stretch the spring 0.40 meter?. 4.8 J. 6.0 J. 9.6 J. 24 J 31. block weighing 15 newtons is pulled to the top of an incline that is 0.20 meter above the ground, as shown.. joules. seconds. watts. newtons 33. The diagram below shows points,, and at or near Earth s surface. s a mass is moved from to, 100. joules of work are done against gravity. If 4.0 joules of work are needed to pull the block the full length of the incline, how much work is done against friction?. 1.0 J. 0.0 J. 3.0 J. 7.0 J What is the amount of work done against gravity as an identical mass is moved from to? J. 173 J J. 273 J 34. When a force moves an object over a rough, horizontal surface at a constant velocity, the work done against friction produces an increase in the object s. weight. momentum. potential energy. internal energy page 7

8 35. s shown in the diagram below, a child applies a constant 20.-newton force along the handle of a wagon which makes a 25 angle with the horizontal. 37. The diagram here shows a 1-kilogram stone being dropped from a bridge 100 meters above a gorge. How much work does the child do in moving the wagon a horizontal distance of 4.0 meters?. 5.0 J. 34 J. 73 J. 80. J 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? s the stone falls, the gravitational potential energy of the stone. decreases. increases. remains the same 38. n object with a mass of 10.0 kilograms is moving at a speed of 5.00 meters per second. The kinetic energy of the mass is joules joules. 125 joules. 250 joules. 1,500 joules. 7,500 joules. 15,000 joules. 75,000 joules 39. 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 8

9 40. Which graph best represents the relationship between the kinetic energy (KE) of a moving object as a function of its velocity (v)? What is the approximate potential energy of the block at point?. 20 J. 200 J. 300 J. 500 J 44. The diagram pictured shows a spring compressed by a force of 6.0 newtons from its rest position to its compressed position. alculate the spring constant for this spring. [Show all calculations, including equations and substitutions with units.] 41. 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? newton weight is attached to a spring, causing it to stretch, as shown in the diagram. What is the spring constant of this spring?., only., only., only. The gain is the same along all paths. 42. The diagram shown represents a frictionless track. 10-kilogram block starts from rest at point and slides along the track N/m N/m. 20 N/m. 40 N/m s the block moves from point to point, the total amount of gravitational potential energy changed to kinetic energy is approximately. 5 J. 20 J. 50 J. 500 J page 9

10 46. box weighing newtons is dragged to the top of an incline, as shown in the diagram. The gravitational potential energy of the box at the top of the incline is approximately 48. In the accompanying diagram, a student compresses the spring in a pop-up toy meter J J J J 47. The unstretched spring in the accompanying diagram has a length of 0.40 meter and a spring constant k. weight is hung from the spring, causing it to stretch to a length of 0.60 meter. If the spring has a spring constant of 340 newtons per meter, how much energy is being stored in the spring? J J. 3.4 J. 6.8 J 49. ase your answer(s) to the following question(s) on the information and diagram below, which is drawn to a scale of 1.0 centimeter = 3.0 meters. 650-kilogram roller coaster car starts from rest at the top of the first hill of its track and glides freely. [Neglect friction.] How many joules of elastic potential energy are stored in this stretched spring? k k k. 2.0 k Using one or more complete sentences, compare the kinetic energy of the car at the top of the second hill to its kinetic energy at the top of the third hill. page 10

11 50. Two vacationers walk out on a horizontal pier as shown in the accompanying diagram. s they approach the end of the pier, their gravitational potential energy will. decrease. increase. remain the same page 11

12 Problem-ttic format version c Educide Software Licensed for use by phelipedfernandes@gmail.com Terms of Use at 1/16/ W = Fd; W =(25 N)(6.0 m) W = 150J or 150 N m 350 N/m J PE = mg h; J Internal energy increases. The total mechanical energy increases. k = 170 N/m PE s = 0.42 J kinetic energy

13 Teacher s Key Page F = kx; 60 N = k (0.040); k = 150N/m; The car s KE is less.