Download Introduction to Physical Science

1
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.
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?
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Energy of Objects in Motion
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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.
14. At what time on the graph below does the object start to experience negative work being
done on it? Explain.
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?
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Energy of Objects in Motion
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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?
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Energy of Objects in Motion
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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 a 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.
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8th Grade PSI
Energy of Objects in Motion
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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.
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8th Grade PSI
Energy of Objects in Motion
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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
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Energy of Objects in Motion
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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?
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8th Grade PSI
Energy of Objects in Motion
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Answers:
1) Energy is the ability to do work.
2) An applied force and a displacement.
3) Work is the product of the force applied and the displacement of the object.
4) It would increase
5) Positive, the force applied is in the direction of the displacement
6) positive, the object is accelerating
7) 10 J, the air through air resistance
8) Mechanical and Non-Mechanical
9) The energy of an object due to its position or motion.
10) The energy of an object that is not due to its position or motion, but rather is energy at the
atomic level.
11) It would remain constant
12) Air resistance is doing work against the man’s displacement (negative work) and therefore
causing the velocity to decrease.
13) No work is being done because the velocity is constant.
14) Negative work is being done because the velocity is decreasing.
15) 0 J
16) Potential and Kinetic energy
17) Electric and Nuclear energy
18) mass and velocity
19) it increases
20) Since the mouse has less mass than the elephant, it has to have a larger velocity in order to
have the same kinetic energy.
21) 4 times larger
22) it is doubled
23) 360 J
24) 1,200 J
25) 37.500 J
26) Joule (J)
27) when the object is not moving (velocity equals 0)
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Energy of Objects in Motion
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28) it decreases
29) it reduces by four times
30) it is cut in half
31) 162 J
32) 25 J
33) 7 times larger
34) mass, gravity, and weight
35) increases
36) decreases
37) decreases
38) cut in half
39) 49 J
40) 19,600 J
41) 110, 250 J
42) 19.6 J
43) 88.2 J
44) Joules (J)
45) when the height is zero
46) increases
47) doubled
48) 735,000 J
49) 22.8 J
50) 22.2 J
51) 47, 040 J
52) 3.7 J
53) The spring constant and the amount that the spring is stretched or compressed.
54) The “elasticity” of an object (how much an object stretches when an amount of force is
applied).
55) Neither, both will have the same amount of potential energy.
56) The spring stretched 2X will have 4X more Elastic Potential Energy since the distance of
stretch is squared.
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Energy of Objects in Motion
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57) 4X
58) 250 J
59) 31.3 J
60) 3.1 J
61) The length of a spring when it is not stretched
62) B – spring constant is twice as large
63) 0 J
64) 100 J
65) 62.5 J
66) 4.7 J
67) A – it is at the highest height
68) None – there is no spring that is stretched or compressed
69) B – it will be going the fastest because it is at the lowest point
70) All points have the same Total Energy
71) 3 – the person is at the highest point
72) 1 – the springs are stretched the most
73) 2 – the person is going the fastest when he leaves the trampoline
74) All points have the same Total Energy
75) ho – it has the highest height
76) None – there is no spring that is stretched or compressed
77) at the point of contact between h0 and h1 because it is falling from the highest height
78) All points have the same Total Energy
79) A – it is at the highest height
80) None – there is no spring that is stretched or compressed
81) B – it is at the lowest point and all GPE from A is converted into KE
82) All points have the same Total Energy
83) Energy resources that replenish themselves in a timely manner.
84) Energy resources that exist in limited supply and cannot be replenished in a timey manner
85) Wind. Solar, Water, Biomass, Geothermal
86)Fossil fuels and nuclear energy.
87) As the turbine moves it creates kinetic energy.
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Energy of Objects in Motion
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88) As the water falls from it converts from gravitational potential energy into kinetic energy.
As the water flows by the turbine it moves the turbine doing work and creating electricity.
89) Solar Energy
90) Because the amount of time it takes to produce fossil fuels is much larger compared to the
amount of time it takes to consume fossil fuels,
91) Because Carbon Dioxide is produced when it is burned.
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8th Grade PSI
Energy of Objects in Motion