1. Chapter 9: Energy
Material on Final Exam

2. Section 9-1—What is Energy
Objectives
Explain the relationship between energy and work.
Compare kinetic energy and potential energy.
Describe the different forms of energy.

3. Section 9-1—What is Energy
Energy is known by the changes it causes
Energy is the ability to do work.
Work is the transfer of energy.
Work and Energy are closely related: Energy is transferred by a force moving an object through a distance.

4. Section 9-1—What is Energy
Work and energy are both expressed in SI units known as a Joule (J).
How big (or small) is a Joule?
There are J in a calorie
Your food Calories are actually kcal—1000 calories!
A 2000kcal diet would be Joules!

5. Section 9-1—What is Energy
Types of Energy
We break energy down into several categories
Mechanical energy
Kinetic
Potential
Thermal energy
Chemical energy
Electrical energy
Electromagnetic energy
Nuclear energy

6. Section 9.1—What is energy?
Energy can constantly switch forms

7. Section 9-1—What is Energy
Mechanical energy
Mechanical Energy is the energy associated with the motion and position of objects.
Both kinetic energy and potential energy are examples of mechanical energy.
Examples: speeding train
bouncing balls, sprinting athletes,
baseball falling through the air.
FORMULA
ME= (KE+PE)

8. Section 9-1—What is Energy

10. Section 9-1—What is Energy
Math practice
Balls being juggled by a juggler has a potential energy of 20 J and kinetic energy of 600 J. What is the ball’s total mechanical energy?
You try!
Let’s say a pin being juggled by a juggler has a potential energy of 30 J and the kinetic energy of 500 J. What is the pin’s mechanical energy?

11. Section 9-1—What is Energy
A roller coaster has the potential energy of 10,000 J and the kinetic energy of 50,000 J. What is the coaster’s mechanical energy?

12. Section 9-1—What is Energy
A. Kinetic energy
The energy of motion.
All moving objects have kinetic energy.
Kinetic Energy of any moving object depends upon its mass and speed.
FORMULA -
SI Unit = Joule
KE = mv2 2

13. Section 9-1—What is Energy
No formula triangle?
Because of the squared part, we cannot use a formula triangle.
You can rewrite the formulas..
But it’s easier to do the algebra
m = 2(KE) V = 𝟐(𝑲𝑬) 𝒎 v2

14. Section 9-1—What is Energy
Math practice
A 70 kg man is walking at a speed of 2 m/s. What is his kinetic energy?
You try!
A 1400 kg cart moves at 25 m/s. What is the cart’s kinetic energy?

15. Section 9-1—What is Energy
A 50 kg cheetah has a KE of 18,000J. How fast is the cheetah running?

16. ANSWER MUST BE 3 LINES OF TEXT FOR FULL CREDIT!
PROCESS BOX 1
What would you need to do to maximize kinetic energy? What would you need to do to minimize kinetic energy?
ANSWER MUST BE 3 LINES OF TEXT FOR FULL CREDIT!

17. Section 9-1—What is Energy
B. Potential Energy
Potential Energy is energy stored as a result of position or shape.
Examples: rock on a cliff, rubber band, wind up toy.
Gravitational Potential Energy depends on an objects weight (mass) and height.
This type of energy increases when an object is raised to a higher level.
Gravitational potential energy is equal to the amount of work done on an object to lift it a certain height.

18. Section 9-1—What is Energy

19. Section 9-1—What is Energy
FORMULA –
PE = m g h or PE = wh
REMEMBER – weight = force
To get weight, do mass (kg) x gravity

20. Section 9-1—What is Energy
Math practice
What is the gravitational potential energy of a cat that weighs 40 N standing on a table that is 0.8 m above the ground?
You try!
What is the gravitational potential energy of a diver who weighs 500 N standing on a platform that is 10 m off the ground?

21. Section 9-1—What is Energy
What is the gravitational potential energy of a diver who has a mass of 61 kg standing on a platform that is 8 m off the ground?

22. ANSWER MUST BE 3 LINES OF TEXT FOR FULL CREDIT!
PROCESS BOX 2
Where would you put an object to maximize its GPE? Where would GPE be zero?
ANSWER MUST BE 3 LINES OF TEXT FOR FULL CREDIT!

23. Section 9-1—What is Energy
Thermal Energy
Thermal (heat) Energy - is all of the kinetic energy due to random motion of the particles that make up an object.
All matter has thermal energy because all particles are in constant random motion.

24. Section 9-1—What is Energy
Thermal energy and speed
As temperature increases, the atoms move faster.
The faster the atoms move, the higher thermal energy.

25. Section 9-1—What is Energy
Chemical Energy
Chemical Energy is the energy of a chemical compound that changes as its atoms are rearranged.
It is the energy stored in the chemical bonds in compounds.
When the bonds break energy is released.
Examples include:
Gasoline/coal
Food
Wood

26. Section 9-1—What is Energy
Electrical Energy
Electrical Energy is the energy associated with electric charges.
Electric charges can exert forces that do work.
Examples include:
Batteries
lightning

27. Section 9-1—What is Energy
Electromagnetic Energy
Electromagnetic Energy is a form of energy that travels through space in the form of waves.
Sun (visible light)
Stars
Galaxies
Radio waves
X-rays

28. Section 9-1—What is Energy

29. Section 9-1—What is Energy
Nuclear Energy
Nuclear Energy is the energy stored in the nuclei of atoms.
Nuclear fission is a process of releasing energy through splitting nuclei apart.
Nuclear Fusion releases energy when a less massive nuclei combine to form a more massive nucleus.

30. ANSWER MUST BE 2 LINES OF TEXT FOR FULL CREDIT!
PROCESS BOX 3
Explain three different energy forms that would be found in the process of burning wood to boil water to make steam.
ANSWER MUST BE 2 LINES OF TEXT FOR FULL CREDIT!

31. Section 9-1—What is Energy
Objectives
Please answer the following on your objectives sheet
Explain the relationship between energy and work.
Compare kinetic energy and potential energy.
Describe the different forms of energy.

32. Section 9-2 & 9-3—Energy Conversions
Objectives
Describe an energy conversion.
Give examples of energy conversions for the different forms of energy.
Explain how energy conversions make energy useful.
Explain the law of conservation of energy.
Give examples of how thermal energy is always a result of energy conversion.

33. Section 9-2 & 9-3—Energy Conversions
Law of Conservation of Energy
Energy can not be created or destroyed.
Energy can be converted from one form to another.
Any form of energy can change into any other form of energy.

34. Section 9-2 & 9-3—Energy Conversions
In energy conversions, some energy is always lost as heat (Thermal energy).
After energy conversions, you always end up with the same total amount of energy as the original amount of potential energy.

36. Section 9-2—Energy Conversions

37. Section 9-2—Energy Conversions

38. Section 9-2 & 9-3—Energy Conversions
In lighting a match, your muscles use chemical energy moving your hand to strike the match, friction converts some of the matches kinetic energy into thermal energy. The thermal energy triggers a chemical reaction on the match tip, releasing some of the match’s chemical energy. The stored chemical energy is then converted into thermal energy and electromagnetic energy in the flame.

39. Section 9-2 & 9-3—Energy Conversions
Alarm Clock
Battery
Light Bulb
Blender
Hair Dryer
Light & sound energy (electromagnetic)
Electrical energy
Chemical energy
Electrical energy
Light (electromagnetic) & thermal energy
Electrical energy
Kinetic & sound (electromagnetic) energy
Electrical energy
Thermal & sound (electromagnetic) energy
Electrical energy

40. PROCESS BOX 4
Where in a roller coaster would you have all KE? Where would you have all PE?

41. Section 9-2 & 9-3—Energy Conversions
Objectives
Please answer the following on your objectives sheet
Describe an energy conversion.
Give examples of energy conversions for the different forms of energy.
Explain how energy conversions make energy useful.
Explain the law of conservation of energy.
Give examples of how thermal energy is always a result of energy conversion.

42. Section 9.4—Energy Resources
Objectives
Explain the difference between nonrenewable resources and renewable resources.
Name several energy resources.

43. Section 9.4—Energy Resources
Nonrenewable Resources
Nonrenewable resources cannot be replaced or are replaced much more slowly than they are used.
Fossil fuels are nonrenewable energy resources that formed from the remains of organisms that lived long ago.
Examples include: Oil, natural gas, and coal are the most common fossil fuels.

44. Section 9.4—Energy Resources
Burning coal is a common way to generate electrical energy.
Petroleum is used to make gasoline, wax, and plastics.
Natural gas is often used in home heating.
The United States’ primary source of electrical energy is generated by burning fossil fuels.

45. Section 9.4—Energy Resources

46. Section 9.4—Energy Resources
How do we make electricity from these resources?
Electric generators convert the chemical energy in fossil fuels into electrical energy by the process shown below.
An electric generator converts energy of one type into another type of energy.

47. Section 9.4—Energy Resources
Renewable Resources
Renewable resources are naturally replaced more quickly than they are used.
Solar Energy Sunlight can be changed into electrical energy through solar cells.
Energy from Water The potential energy of water in a reservoir can be changed into kinetic energy as the water flows through a dam.
Wind Energy The kinetic energy of wind can turn the blades of a windmill or a wind turbine.

48. Section 9.4—Energy Resources

49. Section 9.4—Energy Resources
Objectives
Please answer the following on your objectives sheet
Explain the difference between nonrenewable resources and renewable resources.
Name several energy resources.