1. Today’s special Project work day Materials & “on task” check
Semester I Exam review project teams and assignments

2. Today’s special HW check - Vocab 15 Test results Video on Energy
Notes 15 Energy
HW I due next time!
Semester Exam review project work day next

3. Energy
PAf.1: Explain how the law of conservation of energy applies to the transformation of various forms of energy (including mechanical energy, electrical energy, chemical energy, light energy, sound energy, and thermal energy).
PAf.2: Explain the factors that determine potential and kinetic energy and the transformation of one to the other.
PAf.3: Explain work in terms of the relationship among the force applied to an object, the displacement of the object, and the energy transferred to the object.
PAf.4: Use the formula W = Fd to solve problems related to work done on an object.
PAa.1: Generate hypotheses on the basis of credible, accurate, and relevant sources of scientific information.
PAa.2: Use appropriate laboratory apparatuses, technology, and techniques safely and accurately when conducting a scientific investigation.
PAa.9: Use appropriate safety procedures when conducting investigations.

4. We must always change, renew, rejuvenate ourselves; otherwise we harden.
Johan Wolfgang von Goethe
Fact: The average lifespan of a major league baseball: 7 pitches.

5. Energy has different forms.
Energy and Work
Energy has different forms.
The sun gives off energy in the form of heat and light.

6. Energy has different forms.
Energy and Work
Energy has different forms.
The sun gives off energy in the form of heat and light.
Plants convert sunlight into food.

7. Energy has different forms.
Energy and Work
Energy has different forms.
The sun gives off energy in the form of heat and light.
Plants convert sunlight into food.
People convert food energy into muscle movement.

8. Kinetic Energy
Doubling the mass in the formula doubles the kinetic energy.
Doubling the speed quadruples the kinetic energy.

9. Kinetic Energy
Calculating Kinetic Energy
A 0.10-kilogram bird is flying at a constant speed of 8.0 m/s. What is the bird’s kinetic energy?

10. Kinetic Energy Read and Understand What information are you given?
What unknown are you trying to calculate?

11. Kinetic Energy Read and Understand What information are you given?
What unknown are you trying to calculate?

12. Kinetic Energy
Plan and Solve
What equation contains the given quantities and the unknown?
Substitute the known values in the formula for KE.

13. Kinetic Energy
Plan and Solve
What equation contains the given quantities and the unknown?
Substitute the known values in the formula for KE.

14. Kinetic Energy
Look Back and Check
Is your answer reasonable?

15. Kinetic Energy Look Back and Check
Is your answer reasonable?
It seems reasonable, because the bird has a low mass, so it would not have much kinetic energy.

16. Potential Energy
Gravitational Potential Energy
Potential energy that depends upon an object’s height is called gravitational potential energy.
This type of potential energy increases when an object is raised to a higher level.

17. Potential Energy
The unit for mass is kilograms.
The unit for height is meters.
Acceleration due to gravity, g, has a value in SI units of 9.8 m/s2 on Earth.
The unit for gravitational potential energy is joules.

18. Potential Energy
What is the potential energy relative to the water surface of a diver at the top of a 10.0-meter-high diving platform. Suppose she has a mass of 50.0 kilograms.
PE = mgh
= (50.0 kg)(9.8 m/s2)(10.0 m)
= 4900 kg•m2/s2 = 4900 J

20. How are work and energy related?
Assessment Questions
How are work and energy related?
Energy is the rate of doing work.
Work is a form of energy.
Work is the transfer of energy.
Energy is created by work.

21. How are work and energy related?
Assessment Questions
How are work and energy related?
Energy is the rate of doing work.
Work is a form of energy.
Work is the transfer of energy.
Energy is created by work. ANS: C

22. Assessment Questions
A moving object with a mass of 10 kg has 320 J of kinetic energy due to its motion. How fast is the object moving?
64 m/s
32 m/s
8 m/s
10 m/s

23. Assessment Questions
A moving object with a mass of 10 kg has 320 J of kinetic energy due to its motion. How fast is the object moving?
64 m/s
32 m/s
8 m/s
10 m/s
ANS: C

24. Which of these is an example of elastic potential energy?
Assessment Questions
Which of these is an example of elastic potential energy?
a bow prepared to release an arrow
a rubber ball thrown into the air
a book about to fall from a table
a truck pulling a trailer

25. Which of these is an example of elastic potential energy?
Assessment Questions
Which of these is an example of elastic potential energy?
a bow prepared to release an arrow
a rubber ball thrown into the air
a book about to fall from a table
a truck pulling a trailer ANS: A

26. Assessment Questions
A small airplane and a helicopter have identical masses. If the airplane’s altitude compared to the ground is three times that of the helicopter, how much more gravitational potential energy does the airplane have than the helicopter?
0.333 times as much
3 times as much
6 times as much
9 times as much

27. Assessment Questions
A small airplane and a helicopter have identical masses. If the airplane’s altitude compared to the ground is three times that of the helicopter, how much more gravitational potential energy does the airplane have than the helicopter?
0.333 times as much
3 times as much
6 times as much
9 times as much ANS: B

28. The energy stored in the bonds between atoms of a compound is called
Assessment Questions
The energy stored in the bonds between atoms of a compound is called
electromagnetic energy.
chemical energy.
atomic energy.
thermal energy.

29. The energy stored in the bonds between atoms of a compound is called
Assessment Questions
The energy stored in the bonds between atoms of a compound is called
electromagnetic energy.
chemical energy.
atomic energy.
thermal energy. ANS: B

30. Today’s special Work day-Exam Review project teams
Finish binder checks
HW I check

31. Today’s special
Orion
HW I check; Q & A
Energy Lab: due next!
E.S.B.

32. Today’s special Energy lab due (turn in now on front desk) Some notes
HW II due next
Energy graphic organizer
Shuttle movie
Exam review teams
Rubber band cars

33. Energy Conversion
The process of changing energy from one form to another is energy conversion. The striking of a match is a good example.
Muscles use chemical energy to move the match.
Friction between the match and the matchbox converts kinetic energy into thermal energy.
Chemical energy is converted into thermal energy and electromagnetic energy in the flame.

34. Conservation of Energy
What is the law of conservation of energy?
The law of conservation of energy states that energy cannot be created or destroyed.

35. Conservation of Energy
The work done by friction changes kinetic energy into thermal energy.
Friction within machinery reduces efficiency. Friction is a major cause of energy consumption in cars and factories.
In many cases, most of a falling object’s potential energy is converted into thermal energy because of air resistance.

36. Energy Conversions
One of the most common energy conversions is between potential energy and kinetic energy.
An avalanche brings tons of snow from the top of a mountain to the valley floor.
The elastic potential energy of a compressed spring is converted into kinetic energy as the spring expands.
Energy conversions can go from kinetic to potential energy or from potential to kinetic energy.

37. Energy Conversions
Pendulum clocks use pendulums to maintain accurate time.
The time it takes for a pendulum to swing back and forth once is precisely related to its length.

38. Energy Conversions
The law of conservation of energy applies to any mechanical process. If friction can be neglected, the total mechanical energy remains constant.

39. Energy Conversions
Conservation of Mechanical Energy
At a construction site, a 1.50-kg brick is dropped from rest and hits the ground at a speed of 26.0 m/s. Assuming air resistance can be ignored, calculate the gravitational potential energy of the brick before it was dropped.

40. Energy Conversions Read and Understand What information are you given?
What unknown are you trying to calculate?

41. Energy Conversions Read and Understand What information are you given?
What unknown are you trying to calculate?

42. Energy Conversions
Plan and Solve
What equations or formulas contain the given quantities and the unknown?

43. Energy Conversions
Plan and Solve
What equations or formulas contain the given quantities and the unknown? Because the brick falls without air resistance, the conservation of mechanical energy equation can be used.

44. Energy Conversions Plan and Solve
You will also need to use the formula for kinetic energy (KE). Note that the KE at the beginning is zero because the brick has not yet begun to fall. Also, when the brick hits the ground, its potential energy is zero. Substitute these values into the conservation of energy formula.

45. Energy Conversions
Plan and Solve
Substitute the formula for KE Substitute the known values and calculate the PE.

46. Energy Conversions
Plan and Solve
Substitute the formula for KE Substitute the known values and calculate the PE.

47. Energy Conversions
Look Back and Check
Is your answer reasonable?

48. Energy Conversions Look Back and Check
Is your answer reasonable?
Check the answer by finding the initial height of the brick, using PE = 507 J = mgh. Substituting in m and g gives h = 34.5 m. This is a reasonable height for an object in free fall to reach a speed of 26.0 m/s.

49. Energy Conversions
A pendulum with a 1.0-kg weight is set in motion from a position 0.04 m above the lowest point on the path of the weight. What is the kinetic energy of the pendulum at the lowest point? (Hint: Assume there is no friction.) Answer:

50. Energy Conversions
A pendulum with a 1.0-kg weight is set in motion from a position 0.04 m above the lowest point on the path of the weight. What is the kinetic energy of the pendulum at the lowest point? (Hint: Assume there is no friction.) Answer: (PE)beginning = mgh
= (1.0 kg)(9.8 m/s2)(0.04 m) = 0.4 J;
at the beginning, KE = 0, and at the lowest point, PE = 0;
therefore (PE)beginning = (KE)end = 0.4 J

51. Energy and Mass
Albert Einstein developed his special theory of relativity in This theory included the now-famous equation E = mc2.
E is energy, m is mass, and c is the speed of light.
The speed of light is an extremely large number, 3.0 × 108 meters per second.
A tiny amount of matter can produce an enormous amount of energy.

52. Energy and Mass
In nuclear fission and fusion reactions, however, large amounts of energy are released by the destruction of very small amounts of matter.
The law of conservation of energy has been modified to say that mass and energy together are always conserved.

53. What energy conversion occurs as a result of friction?
Assessment Questions
What energy conversion occurs as a result of friction?
chemical energy to thermal energy
kinetic energy to potential energy
kinetic energy to thermal energy
potential energy to thermal energy

54. What energy conversion occurs as a result of friction?
Assessment Questions
What energy conversion occurs as a result of friction?
chemical energy to thermal energy
kinetic energy to potential energy
kinetic energy to thermal energy
potential energy to thermal energy ANS: C

55. Assessment Questions
At what point in a pendulum’s swing does it have maximum kinetic energy?
the highest point of the swing
the lowest point of the swing
halfway between the lowest and highest point
same at all positions of the swing

56. Assessment Questions
At what point in a pendulum’s swing does it have maximum kinetic energy?
the highest point of the swing
the lowest point of the swing
halfway between the lowest and highest point
same at all positions of the swing ANS: C

57. Assessment Questions
Based on Einstein’s equation for the equivalence of energy and mass, how much energy is produced by the conversion of 1 kilogram of mass to energy?
3x103 J
3x105 J
9x105 J
9x1013 J

58. Assessment Questions
Based on Einstein’s equation for the equivalence of energy and mass, how much energy is produced by the conversion of 1 kilogram of mass to energy?
3x103 J
3x105 J
9x105 J
9x1013 J ANS: D

59. Assessment Questions
According to the law of conservation of mass, energy can be converted from one from to another but not created or destroyed. True False

60. Assessment Questions
According to the law of conservation of mass, energy can be converted from one from to another but not created or destroyed. True False
ANS: F, law of conservation of energy

61. Nonrenewable Energy Resources
What are the major nonrenewable sources of energy?
Nonrenewable energy resources exist in limited quantities and, once used, cannot be replaced except over the course of millions of years.
Nonrenewable energy resources include oil, natural gas, coal, and uranium.

62. Renewable Energy Resources
What are the major renewable sources of energy?
Renewable energy resources are resources that can be replaced in a relatively short period of time.
Renewable energy resources include hydroelectric, solar, geothermal, wind, biomass, and, possibly in the future, nuclear fusion.

63. Renewable Energy Resources
Hoover Dam was built across the Colorado River on the Arizona-Nevada border.
This 221-meter-tall structure can generate over 2 million kilowatts of power.

64. Renewable Energy Resources
Other Renewable Resources
The chemical energy stored in living things is called biomass energy. Biomass can be converted directly into thermal energy or converted into a high-energy alcohol fuel.
A hydrogen fuel cell generates electricity by reacting hydrogen with oxygen. Hydrogen fuel cells can be used to convert energy from renewable resources.

65. World Energy Use
Using Tables What was the world’s largest source of energy in 1991? In 2000? Answer:

66. World Energy Use
Using Tables What was the world’s largest source of energy in 1991? In 2000? Answer: Petroleum in both years.

67. World Energy Use
Analyzing Data In general, how did usage change from 1991 to 2000? Answer:

68. World Energy Use
Analyzing Data In general, how did usage change from 1991 to 2000? Answer: Each type of energy use increased between 1991 and 2000.

69. World Energy Use
Graphing Make a circle graph of world energy use by source for the year 2000.

70. World Energy Use
Graphing Make a circle graph of world energy use by source for the year Answer:
Other 1%
Nuclear fission 6%
Hydroelectric power 7%
Petroleum 39%
Petroleum
Coal
Natural gas
Natural gas 23%
Hydroelectric power
Nuclear fission
Other
Coal 24%

71. World Energy Use
Analyzing Data What percentage of world energy use in 2000 was accounted for by fossil fuels? Answer:

72. World Energy Use
Analyzing Data What percentage of world energy use in 2000 was accounted for by fossil fuels? Answer: Approximately 86%.

73. World Energy Use
Predicting How might total world energy use be different in 2020? Explain. Answer:

74. World Energy Use
Predicting How might total world energy use be different in 2020? Explain. Answer: Based on the trend between 1991 and 2000, the total world energy use will likely be significantly higher in 2020 than it was in The percentage of energy resources in the “other” category will increase by 2020.

75. Conserving Energy Resources
How can energy resources be conserved?
Energy resources can be conserved by reducing energy needs and by increasing the efficiency of energy use.

76. Which of the following is a nonrenewable energy resource?
Assessment Questions
Which of the following is a nonrenewable energy resource?
geothermal energy
hydroelectric energy
hydrogen fuel cells
natural gas

77. Which of the following is a nonrenewable energy resource?
Assessment Questions
Which of the following is a nonrenewable energy resource?
geothermal energy
hydroelectric energy
hydrogen fuel cells
natural gas ANS: D

78. What is one of the advantages of hydroelectric power?
Assessment Questions
What is one of the advantages of hydroelectric power?
can be used everywhere
does not cause any environmental problems
uses energy produced by Earth
inexpensive compared to other energy sources

79. What is one of the advantages of hydroelectric power?
Assessment Questions
What is one of the advantages of hydroelectric power?
can be used everywhere
does not cause any environmental problems
uses energy produced by Earth
inexpensive compared to other energy sources ANS: D

80. Which of these actions is not a way to conserve energy resources?
Assessment Questions
Which of these actions is not a way to conserve energy resources?
turn off lights when they are not needed
increase usage of mass transit
reduce the cost of energy production
increase efficiency of appliances

81. Which of these actions is not a way to conserve energy resources?
Assessment Questions
Which of these actions is not a way to conserve energy resources?
turn off lights when they are not needed
increase usage of mass transit
reduce the cost of energy production
increase efficiency of appliances ANS: C

82. Today’s special HW II check Practice test
Semester exam review work time
Rubber band car work time/supply check
Test & car race next time!

83. Today’s special Turn in Practice test on front desk
Test 15 Energy-Take home: due next class
Work time for semester exam review projects
Turn in projects on common drive

84. Today’s special Turn in Practice test on front desk
Test 15 Energy-Take home: due next class
Presentations
Study time/work time

85. Today’s special Turn in test on front desk Presentations
Study time/work time