# Units 5 Review

Energy

1. An object is raised above the ground gaining a certain amount of potential energy. If the same object is raised twice as high it gains __________.

1. four times as much potential energy
2. twice as much potential energy
3. neither of these

Potential Energy (12 seconds)

2. When an object is lifted 10 meters, it gains a certain amount of potential energy. If the same object is lifted 20 meters, its potential energy is _____.
 a. less b. the same c. twice as much d. four times as much e. more than 4 time as much

Potential Energy (12 seconds)

3. A 1000 kg car and a 2000 kg car are hoisted the same distance at constant speed in a gas station. Raising the more massive car requires ____________.
 a. less work b. as much work c. twice as much work. d. four times as much work e. more than 4 times as much work

Potential Energy (12 seconds) | Analysis of Situations Involving External Forces (21 seconds)

4. An object that has kinetic energy must be ____________.
 a. moving b. falling c. at an elevated position d. at rest e. none of these

Kinetic Energy (4 seconds)

5. An object that has potential energy has this energy because of its _____________.
 a. speed b. acceleration c. momentum d. position e. none of these

Potential Energy (12 seconds)

6. An arrow is drawn so that it has 40 J of potential energy. When fired horizontally, the arrow will have a kinetic energy of ________.
 a. less than 40 J b. more than 40 J c. 40 J

Mechanical Energy (15 seconds)

7. A 2 kg mass is held 4 m above the ground. What is the approximate potential energy of the mass with respect to the ground?

 a. 20 J b. 40 J c. 60 J d. 80 J e. none of these

Potential Energy (12 seconds)

8. A 2 kg mass has 40 J of potential energy with respect to the ground. Approximately how far is it located above the ground?
 a. 1 m b. 2 m c. 3 m d. 4 m e. none of these

Potential Energy (12 seconds)

9. A ball is projected into the air with 100 J of kinetic energy which is transformed to gravitational potential energy at the top of its trajectory. When it returns to its original level after encountering air resistance, its kinetic energy is ____________.
 a. less than 100 J b. 100 J c. more than 100 J d. not enough information given

Mechanical Energy Conservation (13 seconds)

10. A woman lifts a box from the floor. She then carries with constant speed to the other side of the room, where she puts the box down. How much work does she do on the box while walking across the floor at constant speed?
 a. zero J b. more than zero J c. more information needed to determine

Definition and Mathematics of Work (10 seconds)

11. A car moving at 50 km/hr skids 20 m with locked brakes. How far will the car skid with locked brakes if it is traveling at 150 km/hr?
 a. 20 m b. 60 m. c. 90 m d. 120 m e. 180 m

Analysis of Situations Involving External Forces (21 seconds)

12. Which has greater kinetic energy, a car traveling at 30 km/hr or a half-as-massive car traveling at 60 km/hr?
 a. the 30 km/hr car b. the 60 km/hr car c. both have the same kinetic energy

Kinetic Energy (4 seconds)

13. 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.

Kinetic Energy (4 seconds) | Mechanical Energy Conservation (13 seconds)

14. A 2500 N pile driver ram falls 10 m and drives a post 0.1 m into the ground. The average impact force on the ram is _________.
 a. 2500 N b. 25000 N c. 250,000 N d. 2,500,000 N

Analysis of Situations Involving External Forces (21 seconds)

15. A person on the edge of a roof throws a ball downward. It strikes the ground with 100 J of kinetic energy. The person throws another identical ball upward with the same initial speed, and this too falls to the ground. Neglecting air resitance, the second ball hits the ground with a kinetic energy of ______________.
 a. 100 J b. 200 J c. less than 100 J d. more than 200 J e. none of these

Mechanical Energy Conservation (13 seconds)

16. A 10 N object moves at 1 m/s. Its kinetic energy is ____________.
 a. 0.5 J b. 1 J c. 10 J d. more than 10 J

Kinetic Energy (4 seconds)

17. A moving object has __________.
 a. speed b. velocity c. momentum d. energy e. all of these

Momentum (7 seconds) | Kinetic Energy (4 seconds)

18. An object at rest may have __________.
 a. speed b. velocity c. momentum d. energy e. all of these

Momentum (7 seconds) | Mechanical Energy (15 seconds)

19. What does an object have when it is moving that it absolutely doesn`t have when at rest?
 a. momentum b. energy c. mass d. inertia e. none of these

Inertia (12 seconds) | Momentum (7 seconds) | Mechanical Energy (15 seconds)

20. If an object has kinetic energy, then it also must have ___________.
 a. impulse b. momentum c. acceleration d. force e. none of these

Momentum (7 seconds) | Kinetic Energy (4 seconds)

21. If the speed of a moving object doubles, then what else doubles?
 a. momentum b. kinetic energy c. acceleration d. all of the above e. none of these

Acceleration (12 seconds) | Momentum (7 seconds) | Kinetic Energy (4 seconds)

22. A popular swinging-balls apparatus consists of an aligned row of identical elastic balls that are suspended by strings so they barely touch each other. When two balls are lifted from one end and released, they strike the row and two balls pop out from the other end. If instead one ball popped out with twice the velocity of the two, this would be violation of conservation of __________.
 a. momentum b. kinetic energy c. both of these d. none of these

Kinetic Energy (4 seconds) | Potential Energy (12 seconds) | Mechanical Energy (15 seconds)

23. A 2 kg mass has a velocity of 4 m/s. The kinetic energy of the mass is ___ Joules.
 a. 4 b. 8 c. 16 d. 32 e. none of these

Kinetic Energy (4 seconds)

24. A car moving at 50 km/hr skids 20 meters with locked brakes. How far will the car skid with locked brakes if it is traveling at 150 km/hr?
 a. 20 m b. 60 m c. 90 m d. 120 m e. 180 m

Analysis of Situations Involving External Forces (21 seconds)

25. A 50 kg diver hits the water below (at a zero height) with a kinetic energy of 5000 Joules. The height from which the diver dove was ____ meters.
 a. 5 b. 10 c. 50 d. 100

Mechanical Energy Conservation (13 seconds)

26. A job is done slowly, and an identical job is done quickly. Both jobs require the same amount of work, but different amounts of ___________.
 a. energy b. power c. both of these d. none of these

Power (13 seconds)

27. Which requires more work: lifting a 50 kg sack vertically 2 meters or lifting a 25 kg sack vertically 4 meters?
 a. lifting the 50 kg sack b. lifting the 25 kg sack c. both require the same amount of work

Definition and Mathematics of Work (10 seconds) | Calculating the Amount of Work Done by Forces (10 seconds)

28. A 50 kg sack is lifted 2 meters in the same time as a 25 kg sack is lifted 4 meters. The power expended in raising the 50 kg sack compared to the power used to lift the 25 kg sack is _________.
 a. twice as much b. half as much c. the same

Power (13 seconds)

29. A TV set is pushed a distance of 2 m with a force of 20 N that is in the same direction as the set moves. How much work is done on the set?
 a. 2 J b. 10 J c. 20 J d. 40 J e. 80 J

Calculating the Amount of Work Done by Forces (10 seconds)

30. It takes 40 J to push a large box 4 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. 4 N b. 10 N c. 40 N d. 160 N e. none of these

Calculating the Amount of Work Done by Forces (10 seconds)

31. Using 1000 J of work, a toy elevator is raised from the ground floor to the second floor in 20 seconds. How much power does the elevator use?
 a. 20 W b. 50 W c. 100 W d. 1000 W e. 20000 W

Calculating the Amount of Work Done by Forces (10 seconds) | Power (13 seconds)

### Problem-Solving:

32. Calculate the work required lift a 2.5-kg object a height of 6.0 meters. PSYW

Calculating the Amount of Work Done by Forces (10 seconds)

33. In the It's All Uphill Lab, a force of 21.2 N is applied parallel to the incline to lift a 3.0-kg loaded cart to a height of 0.45 m along an incline which is 0.636-m long. Determine the work done upon the cart and the subsequent potential energy change of the cart. PSYW

Calculating the Amount of Work Done by Forces (10 seconds) | Analysis of Situations Involving External Forces (21 seconds)

34. An 800-kg car skids to a stop across a horizontal surface over a distance of 45 m. The average force acting upon the car is 7000N, then determine

1. the work done upon the car.
2. the initial kinetic energy of the car.
3. the acceleration of the car.
4. the initial velocity of the car.

Analysis of Situations Involving External Forces (21 seconds)

35. A 50-kg hiker ascends a 40-meter high hill at a constant speed of 1.2 m/s. If it takes 400 s to climb the hill, then determine

1. kinetic energy change of the hiker.
2. the potential energy change of the hiker.
3. the work done upon the hiker.
4. the power delivered by the hiker.

Kinetic Energy (4 seconds) | Potential Energy (12 seconds) | Work (10 seconds) | Power (13 seconds)

36. Neel, whose mass is 75-kg, ascends the 1.6-meter high stairs in 1.2 s. Determine Neel's power rating. PSYW

Work (10 seconds) | Power (13 seconds)

37. A 500-kg roller coaster car starts at a height of 32.0 m. Assuming negligible energy losses to friction and air resistance, determine the PE, KE, and speed of the car at the various locations (A, B, C, D, and E) along the track.
 Location Height (m) PE (J) KE (J) velocity (m/s) Start 32.0 ________ ________ 0 A 28.0 ________ ________ ________ B 11.0 ________ ________ ________ C 20.0 ________ ________ ________ D 5.0 ________ ________ ________ E 15.0 ________ ________ ________ F 0 ________ ________ ________

Kinetic Energy (4 seconds) | Potential Energy (12 seconds) | Mechanical Energy Conservation (13 seconds)

38. Use the information in the above table to explain what is meant when it is said that the "total mechanical energy is conserved."

Mechanical Energy Conservation (13 seconds)

39. Use the work-energy theorem to determine the force required to stop a 1000-kg car moving at a speed of 20.0 m/s if there is a distance of 45.0 m in which to stop it. PSYW

Analysis of Situations Involving External Forces (21 seconds) | Application and Practice Questions (10 seconds)

40. A 60-kg skiier accelerates down an icey hill from an original height of 500 meters. Use the work-energy theorem to determine the speed at the bottom of the hill if

1. no energy is lost or gained due to friction, air resistance and other external forces. PSYW
2. 140000 J of energy are lost due to external forces. PSYW

Analysis of Situations Involving External Forces (21 seconds) | Mechanical Energy Conservation (13 seconds) | Application and Practice Questions (10 seconds)