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Energy of Objects in Motion
Energy
Classwork
1. Define Energy.
2. What are the two things necessary for work to be done on an object?
3. How can you determine the amount of work is being done on an object?
4. What would happen to an object’s velocity if positive work is done on an object?
5. Based on the diagram below, is positive or negative work being done on the object?
Explain.
6. Based on the graph below, is positive or negative work being done on the object?
Explain.
Velocity (m/s)
Velocity vs. Time
6
4
2
0
0
1
2
3
4
5
6
Time (s)
7. A ball is dropped from the roof of the building. The ball initially had 100 J of Energy.
Just as it landed it had 90 J or Energy. How much work was done on the ball as it fell?
What did the work?
8. What are the two major forms of Energy?
9. What is the definition of Mechanical Energy?
10. What is the definition of Non-Mechanical Energy?
Homework
11. What would happen to an object’s velocity if no work was being done on the object?
12. Based on the diagram below, is the object’s speed increasing or decreasing due to Air
Resistance. Explain in terms of work being done on the object.
13. Based on the graph below, which of the following is being done: positive work, negative
work, no work. Explain.
Velocity (m/s)
Velocity vs. Time
2
1.5
1
0.5
0
0
2
4
6
Time (s)
14. At what time on the graph below does the object start to experience negative work being
done on it? Explain.
Velocity vs. Time
Velocity (m/s)
2
1.5
1
0.5
0
0
2
4
6
Time (s)
15. An adult is driving a car which has 50 J of Energy. At the end of the drive the car still
had 50 J of energy. How much work was done on the car during the drive?
16. What are the two forms of Mechanical Energy?
17. Name two forms of Non-Mechanical Energy.
Kinetic Energy
Classwork
18. What two factors does Kinetic Energy depend upon?
19. If an object is accelerating, how does its Kinetic Energy change?
20. If a mouse and an elephant have the same kinetic energy, can you determine which one is
running faster? Explain.
21. If an object’s speed is doubled, how does its Kinetic Energy change?
22. If the mass of an object is doubled, how does its Kinetic Energy change?
23. How much kinetic energy does an 80 kg man have while running at 3 m/s?
24. A 6 kg object has a speed of 20 m/s. What is its kinetic energy?
25. A 1000 kg car’s velocity increases from 5 m/s to 10 m/s. What is the change it the car’s
kinetic Energy?
Homework
26. What is the SI unit for Kinetic Energy?
27. When is the only time that an object has no Kinetic Energy?
28. If an object is decelerating, how does its Kinetic Energy change?
29. If an object’s speed is cut in half, how does its Kinetic Energy change?
30. If the mass of an object is cut in half, how does its Kinetic Energy change?
31. How much kinetic energy does a 4 kg cat have while running at 9 m/s?
32. A 2 kg watermelon is dropped from a roof and is traveling with a speed of 5 m/s just
before it hits the ground. How much Kinetic Energy does the watermelon have at this
moment?
33. A 700 kg horse is running with a velocity of 5 m/s. How much larger is the horse’s
Kinetic Energy compared to a 100 kg man running at the same speed?
Gravitational Potential Energy
Classwork
34. What three factors does Gravitational Potential Energy depend upon?
35. If an object is thrown up in the air, how does its Gravitational Potential Energy change?
36. If an object is falling, how does its Gravitational Potential Energy change?
37. How does your Gravitational Potential Energy change if you are placed on the moon
where gravity is lower than on Earth?
38. If the mass of an object is cut in half, how does its Gravitational Potential Energy
change?
39. A 1 kg ball is thrown up in the air and reaches a height of 5 m. What is its Gravitational
Potential Energy at that moment?
40. A 200 kg boulder is sitting on top of a 10 m high hill. What is the boulder’s Gravitational
Potential Energy?
41. What is the gravitational potential energy of a 450 kg car at the top of a 25 m parking
garage?
42. A 2.0 kg toy falls from 2 m to 1 m. What is the change in GPE?
43. A small, 3 kg weight is moved from a height of 5 m to a height of 8 m. What is the
change in potential energy?
Homework
44. What is the SI unit for Gravitational Potential Energy?
45. When is the only time that an object has no Gravitational Potential Energy?
46. How does your Gravitational Potential Energy change if you are placed on Jupiter where
gravity is larger than on Earth?
47. If the mass of an object is doubled, how does its Gravitational Potential Energy change?
48. A 75 kg skydiver is spotted at a height of 1000 m above the Earth’s surface. How much
Gravitational Potential Energy does the skydiver possess?
49. A placekicker in football is attempting a field goal and kicks 0.75 kg football which hits
the crossbar that is 3.1 m tall. How much Gravitational Potential Energy does the ball
have when it hits the crossbar?
50. The “Green Monster” is the name for the left field wall at Fenway Park and is 11.33 m
tall. How much Gravitational Potential Energy does a 0.2 kg baseball have when it just
clears the wall?
51. An 80 kg person falls 60 m off of a waterfall. What is her change in GPE?
52. A 0.25 kg book falls off a 2 m shelf on to a 0.5 m chair. What was the change in GPE?
Elastic Potential Energy
Classwork
53. What two factors does Elastic Potential Energy depend upon?
54. Define the term spring constant?
55. The same spring is stretched by 1 meter and then compressed by 1 meter. In which case
will the spring have more Elastic Potential Energy stored in it? Explain.
56. Two identical springs are stretched. Spring A is stretched 1 meter while spring B is
stretched 2 meters. Which spring will have more Elastic Potential Energy stored in it?
Explain.
57. If a spring is stretched twice as far (as in #56), how many times larger is the Elastic
Potential Energy that is stored in it?
58. A spring with a spring constant of 500 N/m is stretched 1 meter in length. How much
Elastic Potential Energy does the spring have stored in it?
59. A spring with a spring constant of 250 N/m is stretched 0.5 meters. How much Elastic
Potential Energy does the spring have stored in it?
60. A spring with a spring constant of 100 N/m is compressed by 0.25 meters. How much
Elastic Potential Energy does it have stored in it?
Homework
61. Define the term “Relaxed Length”.
62. Two springs are stretched to the same distance. If spring A has a spring constant of 200
N/m and spring B has a spring constant of 400 N/m, which spring has more Elastic
Potential Energy stored in it? Explain.
63. A spring with a spring constant of 100 N/m is not stretched. How much Elastic Potential
Energy does the spring have stored in it?
64. A spring with a spring constant of 200 N/m is stretched 1 meter in length. How much
Elastic Potential Energy does the spring have stored in it?
65. A spring with a spring constant of 500 N/m is compressed 0.5 meters. How much Elastic
Potential Energy does the spring have stored in it?
66. A rubber band with a spring constant of 150 N/m is stretched by 0.25 meters. How much
Elastic Potential Energy does it have stored in it?
Conservation of Energy
Classwork
Questions 67 – 70 refer to the diagram below
67. At which position does the block have maximum Gravitational Potential Energy?
Explain.
68. At which position does the block have maximum Elastic Potential Energy? Explain.
69. At which position does the block have maximum Kinetic Energy? Explain.
70. At which position does the block have maximum Total Energy? Explain.
Questions 71 – 74 refer to the diagram below
71. At which position does the man have maximum Gravitational Potential Energy? Explain.
72. At which position does the man have maximum Elastic Potential Energy? Explain.
73. At which position does the man have maximum Kinetic Energy? Explain.
74. At which position does the man have maximum Total Energy? Explain.
Homework
Questions 75-78 refer to the diagram below
75. At which position does the ball have maximum Gravitational Potential Energy? Explain.
76. At which position does the ball have maximum Elastic Potential Energy? Explain.
77. At which position does the ball have maximum Kinetic Energy? Explain.
78. At which position does the ball have maximum Total Energy? Explain.
Questions 79-82 refer to the diagram below
79. At which position does the car have maximum Gravitational Potential Energy? Explain.
80. At which position does the car have maximum Elastic Potential Energy? Explain.
81. At which position does the car have maximum Kinetic Energy? Explain.
82. At which position does the car have maximum Total Energy? Explain.
Types of Energy Resources
Classwork
83. Define Renewable Resource.
84. Define Non-Renewable Resource.
85. List two examples of a Renewable Energy Resource.
86. List two examples of a Non-Renewable Energy Resource.
Homework
87. How does a turbine convert Kinetic Energy of its source into Electrical Energy?
88. How does a hydroelectric power plant transfer both Potential and Kinetic Energy into
Electric Energy?
89. What type of Energy resource does not use a turbine to convert Mechanical Energy into
Electrical Energy?
90. Why are Fossil Fuels considered to be non-renewable energy resources?
91. Why are Fossil Fuels not considered clean energy resources?