SLIDE 1
1 Define Energy.
Slide 4 / 113
2 What two things are necessary for work to be done on an object?
Slide 5 / 113
3 How can you determine the amount of work done
- n an object?
8th Grade Energy of Objects in Motion Classwork-Homework - - PDF document
8th Grade Energy of Objects in Motion Classwork-Homework - - PDF document
Slide 1 / 113 Slide 2 / 113 8th Grade Energy of Objects in Motion Classwork-Homework 2015-08-25 www.njctl.org Slide 3 / 113 Classwork #1: Energy Slide 4 / 113 1 Define Energy. Slide 5 / 113 2 What two things are necessary for work to be
SLIDE 2
SLIDE 3
4 What would happen to an object’s velocity if positive work was done on an object?
Slide 7 / 113
5 Based on the diagram below, is positive or negative work being done on the object? Explain.
Slide 8 / 113
6 Based on the graph below, is positive or negative work being done on the object? Explain.
Slide 9 / 113
SLIDE 4
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.
- a. How much work was done on the ball as it fell?
- b. What did the work?
Slide 10 / 113
8 What are the two major forms of energy?
Slide 11 / 113
9 What is the definition of mechanical energy?
Slide 12 / 113
SLIDE 5
10 What is the definition of non-mechanical energy?
Slide 13 / 113
Homework: Energy
Slide 14 / 113
11 What would happen to an object’s velocity if no work was done on the object?
Slide 15 / 113
SLIDE 6
12 Based on the diagram below, is the person’s speed increasing or decreasing due to air resistance. Explain in terms of work being done on the person.
Slide 16 / 113
13 At what time on the graph below does the object start to experience negative work being done on it? Explain.
Slide 17 / 113
14 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?
Slide 18 / 113
SLIDE 7
15 What are the two forms of mechanical energy?
Slide 19 / 113
16 Name two examples of non-mechanical energy.
Slide 20 / 113
Classwork #2: Kinetic Energy
Slide 21 / 113
SLIDE 8
17 What two factors does kinetic energy depend upon?
Slide 22 / 113
18 If an object is accelerating, how does its kinetic energy change? Justify your answer.
Slide 23 / 113
19 If a mouse and an elephant have the same kinetic energy, can you determine which one is running faster? Explain.
Slide 24 / 113
SLIDE 9
20 If an object’s speed is doubled, how does its kinetic energy change?
Slide 25 / 113
21 If the mass of an object is doubled, how does its kinetic energy change?
Slide 26 / 113
22 How much kinetic energy does an 80 kg man have while running at 3 m/s? Show your work.
Slide 27 / 113
SLIDE 10
23 A 6 kg object has a speed of 20 m/s. What is its kinetic energy? Show your work.
Slide 28 / 113
24 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? Show your work.
Slide 29 / 113
25 What is the SI unit for kinetic energy?
Slide 30 / 113
SLIDE 11
Homework: Kinetic Energy
Slide 31 / 113
26 When is the only time that an object has no k inetic energy?
Slide 32 / 113
27 If an object is decelerating, how does its kinetic energy change?
Slide 33 / 113
SLIDE 12
28 How can a more massive object have the same kinetic energy as a less massive object ?
Slide 34 / 113
29 If an object’s speed is cut in half, how does its kinetic energy change?
Slide 35 / 113
30 If the mass of an object is cut in half, how does its kinetic energy change?
Slide 36 / 113
SLIDE 13
31 How much kinetic energy does a 4 kg cat have while running at 9 m/s? Show your work.
Slide 37 / 113
32 A 2 kg watermelon is dropped from a roof and has a speed of 5 m/s just before it hits the ground. How much kinetic energy does the watermelon have at this moment? Show your work.
Slide 38 / 113
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?
Slide 39 / 113
SLIDE 14
Classwork #3: Gravitational Potential Energy
Slide 40 / 113
34 What three factors does gravitational potential energy depend upon?
Slide 41 / 113
35 If an object is thrown up in the air, how does its gravitational potential energy change? Explain.
Slide 42 / 113
SLIDE 15
36 If an object is falling, how does its gravitational potential energy change? Explain.
Slide 43 / 113
37 How does your gravitational potential energy change if you are placed on the moon where gravity is lower than on Earth?
Slide 44 / 113
38 If the mass of an object is cut in half, how does its gravitational potential energy change?
Slide 45 / 113
SLIDE 16
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? Show your work.
Slide 46 / 113
40 A 200 kg boulder is sitting on top of a 10 m high
- hill. What is the boulder’s gravitational potential
energy? Show your work.
Slide 47 / 113
41 What is the gravitational potential energy of a 450 kg car at the top of a 25 m parking garage? Show your work.
Slide 48 / 113
SLIDE 17
42 A 2.0 kg toy falls from 2 m to 1 m. What is the change in GPE? Show your work.
Slide 49 / 113
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? Show your work.
Slide 50 / 113
Homework: Gravitational Potential Energy
Slide 51 / 113
SLIDE 18
44 When is the only time that an object has no gravitational potential energy?
Slide 52 / 113
45 How does your gravitational potential energy change if you are placed on Jupiter where gravity is larger than on Earth?
Slide 53 / 113
46 If the mass of an object is doubled, how does its gravitational potential energy change?
Slide 54 / 113
SLIDE 19
47 What is the SI unit for gravitational potential energy?
Slide 55 / 113
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? Show your work.
Slide 56 / 113
49 A placekicker in football is attempting a field goal and kicks a 0.75 kg football. The football hits the crossbar that is 3.1 m tall. How much gravitational potential energy does the ball have when it hits the crossbar? Show your work.
Slide 57 / 113
SLIDE 20
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? Show your work.
Slide 58 / 113
51 An 80 kg person falls 60 m off of a waterfall. What is her change in GPE? Show your work.
Slide 59 / 113
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? Show your
work.
Slide 60 / 113
SLIDE 21
Classwork #4: Elastic Potential Energy
Slide 61 / 113
53 What two factors does elastic potential energy depend upon?
Slide 62 / 113
54 Define the term spring constant?
Slide 63 / 113
SLIDE 22
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.
Slide 64 / 113
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.
Slide 65 / 113
57 If a spring is stretched three times as far, by what factor does its elastic potential energy change? Does it increase or decrease?
Slide 66 / 113
SLIDE 23
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? Show your work.
Slide 67 / 113
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? Show your work.
Slide 68 / 113
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? Show your work.
Slide 69 / 113
SLIDE 24
Homework: Elastic Potential Energy
Slide 70 / 113
61 What is meant when a spring has a "relaxed" length?
Slide 71 / 113
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.
Slide 72 / 113
SLIDE 25
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?
Slide 73 / 113
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? Show your work.
Slide 74 / 113
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? Show your work.
Slide 75 / 113
SLIDE 26
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? Show your work.
Slide 76 / 113
Classwork #5: Conservation of Energy
Slide 77 / 113
Questions 67 - 71 refer to the diagram below, which shows a block starting from rest at 30 m.
Slide 78 / 113
SLIDE 27
67 At which position does the block have maximum gravitational potential energy? Explain.
Slide 79 / 113
68 At which position does the block have maximum elastic potential energy? Explain.
Slide 80 / 113
69 At which position does the block have maximum kinetic energy? Explain.
Slide 81 / 113
SLIDE 28
70 At which position does the block have maximum total energy? Explain.
Slide 82 / 113
71 Suppose the block has a mass of 10 kg. Show your work for the following questions.
- a. What is the block's kinetic energy at position B
if its velocity is 19.8 m/s?
- b. What is the block's gravitational potential
energy at position B?
- c. Using your answers from (a) and (b), determine
the block's total energy at position B.
Slide 83 / 113
Questions 72 – 75 refer to the diagram below that shows a person jumping on a trampoline.
Slide 84 / 113
SLIDE 29
72 At which position does the person have maximum gravitational potential energy? Explain.
Slide 85 / 113
73 At which position does the trampoline have maximum elastic potential energy? Explain.
Slide 86 / 113
74 At which position does the person have maximum kinetic energy? Explain.
Slide 87 / 113
SLIDE 30
75 At which position does the person have maximum total energy? Explain.
Slide 88 / 113
Homework: Conservation of Energy
Slide 89 / 113
Questions 76-80 refer to the diagram below which shows a ball dropped from rest at a height of h0.
Slide 90 / 113
SLIDE 31
76 At which position does the ball have maximum gravitational potential energy? Explain.
Slide 91 / 113
77 At which position does the ball have maximum elastic potential energy? Explain.
Slide 92 / 113
78 At which position does the ball have maximum kinetic energy? Explain.
Slide 93 / 113
SLIDE 32
79 At which position does the ball have maximum total energy? Explain.
Slide 94 / 113
80 The amount of total energy the ball possesses is 0.14 J. The mass of the ball is 0.005 kg. Use this information to answer the following:
- a. How much gravitational potential energy does
the ball possess at h 1= 1.5 m? Show your work.
- b. How much kinetic energy does the ball
possess at h1= 1.5 m? Show your work. (Hint: Use the total energy and GPE of the ball.)
Slide 95 / 113
Questions 81-86 refer to the diagram below, which shows a roller coaster cart that starts from rest at a height of 30m.
Slide 96 / 113
SLIDE 33
81 At which position does the car have maximum gravitational potential energy? Explain.
Slide 97 / 113
82 At which position does the car have maximum elastic potential energy? Explain.
Slide 98 / 113
83 At which position does the car have maximum kinetic energy? Explain.
Slide 99 / 113
SLIDE 34
84 Where does the car have both GPE and KE, but more GPE? Explain.
Slide 100 / 113
85 At which position does the car have maximum total energy? Explain.
Slide 101 / 113
86 The car has a mass of 500 kg and moves with a speed of 9.9 m/s at position C. What is the total energy of the car? (Hint: the car possesses KE and GPE at position C. Also remember that TE is the sum of KE and PE.)
Slide 102 / 113
SLIDE 35
Classwork #6: Types of Energy Resources
Slide 103 / 113
87 What is the difference between renewable resources and non-renewable resources?
Slide 104 / 113
88 List two examples of a renewable energy resource.
Slide 105 / 113
SLIDE 36
89 List two examples of a non-renewable energy resource.
Slide 106 / 113
90 Explain how one of the energy resources we talked about in class demonstrates the law of conversation of energy.
Slide 107 / 113
Homework: Types of Energy Resources
Slide 108 / 113
SLIDE 37
91 Explain the role of a turbine in "creating" electrical energy.
Slide 109 / 113
92 How does a hydroelectric power plant transfer both potential and kinetic energy into electric energy?
Slide 110 / 113
93 What type of energy resource does not use a turbine to convert mechanical energy into electrical energy?
Slide 111 / 113
SLIDE 38