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Section 1 What Is Energy?

H.W.-type your homework here

Warm-up #40- page 238

Look at the picture on page 238 and read the caption. A. What form of energy does the car use?

B. What types of energy have you used today?

Teacher notes: pass out the student handout. Students fill in the answers while watching this power point.

Chapter 9



S8P2. Students will be familiar with the forms and transformations of energy. a. Explain energy transformation in terms of the Law of Conservation of Energy. b. Explain the relationship between potential and kinetic energy. c. Compare and contrast the different forms of energy (heat, light, electricity, mechanical motion, sound) and their characteristics.

GPS



Energy and Work: Working Together

1. Energy is the ability to do work.

• Work is done when a force causes an object to move in the direction of the force.

2. Work is a transfer of energy.

3. Energy and work are expressed in units of joules (J).

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Section 1 What Is Energy?Chapter 9

4.




Kinetic Energy

4. Energy is transferred from the first object to the second object

5. Kinetic energy is the energy of motion. All moving objects have kinetic energy.

6. Kinetic Energy Depends on Mass and Velocity If you know an object’s mass (m) and its velocity (v), you can calculate the object’s kinetic energy with the following equation:

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kinetic energy =

mv 2

2



7. & 8. Kinetic Energy

Chapter 9

Click below to watch the Visual Concept.

Visual ConceptVisual Concepts Kinetic.mht

7. The greater the mass, the greater the kinetic energy

8. The more kinetic energy, the greater the damage.


Section 1 What Is Energy?Potential Energy

Not all energy has to do with motion. 9. Potential energy is the energy an object has because of its position, shape, or condition.

Once the ball or the arrow is released, the stored energy is converted to kinetic energy.


Visual Concepts potential.mht

Potential Energy


10. When you lift an object, energy is transferred to the object, which gives the object gravitational potential energy.




Mechanical Energy

11. Mechanical energy is the total energy of motion and position of an object. Both kinetic energy and potential energy are kinds of mechanical energy.

12. The equation to find mechanical energy is:

mechanical energy potential energy kinetic energy ME = PE + KE

Chapter 9



13-15. The kinetic energy decreases as the ball rises because it slows down. When the ball reaches the highest point, it stops and has maximum potential energy. As the ball drops, it has the greatest kinetic energy the closer it gets to her hand.


Section 2 Energy ConversionsChapter 9

As the skateboarder on the next slide travels up and down the half-pipe, his energy changes back and forth between kinetic energy and potential energy


Complete the Jumping Frog activity on the laminated sheet. Answer questions 16-19 when you have completed this activity.




Other Forms of Energy

• Thermal Energy is all of the kinetic energy due to random motion of the particles that make up an object.

• All matter is made up of particles that are always in random motion. So, all matter has thermal energy.

• Thermal energy increases as temperature increases and increases as the number of particles increases.

Chapter 9


Section 1 What Is Energy?Chapter 9

27. What are the small particles that make up matter called?

When the particles move faster, they have greater kinetic energy



Other Forms of Energy, continued

• Chemical Energy is the energy of a chemical compound that changes as its atoms are rearranged.

28. Chemical energy is a form of potential energy because it depends on the position and arrangement of the atoms in a compound.

• The energy in food is chemical energy.

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• Electrical Energy is the energy of moving electrons. Electrical energy can be thought of as potential energy that is used when you plug in an electrical appliance and use it.

• Sound Energy is caused by an object’s vibrations. The object’s vibrations transmit some kinetic energy to the air particles, which also vibrate. These vibrations transmit sound energy.

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• Light Energy is produced by the vibrations of electrically charged particles.

• Nuclear Energy is energy that comes from changes in the nucleus of an atom. Nuclear energy can be produced when nuclei are joined in a fusion reaction or when a nucleus is split apart in a fission reaction.

Chapter 9


Section 2 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 role of machines in energy conversions.

Chapter 9



Kinetic Energy and Potential Energy

29. An energy conversion is a change from one form of energy to another. Any form of energy can change into any other form of energy.

• .

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Section 3 Conservation of Energy

30. The Law of Conservation of Energy states that energy cannot be created or destroyed, it always changes from one form to another.

• Energy can be converted from one form to another. But all of the different forms of energy in a system always add up to the same total amount of energy.

• Thermal energy is always released when energy is transferred or converted.

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Law of Conservation of energy



Kinetic Energy and Potential Energy, continued

• Elastic Potential Energy Stretching a rubber band stores elastic potential energy in the rubber band.

• When you let the rubber band go, it goes back to its original shape. It releases its stored-up potential energy as it does so.

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Conversions Involving Chemical Energy

• Chemical energy is stored in the food you eat. Your body uses this chemical energy to function.

• Energy Conversion in Plants The chemical energy in the food you eat comes from the sun’s energy. Plants use photosynthesis to convert light energy into chemical energy, as shown on the next slide.

Chapter 9





Conversions Involving Chemical Energy, continued

• The Process Continues Plants change light energy into chemical energy. The chemical energy in the food you eat is changed into another kind of chemical energy that your body can use.

• Your body then uses that energy to give you kinetic energy that you use in everything you do.

Chapter 9




Why Energy Conversions Are Important

• Energy conversions are needed for everything we do. Heating our homes, getting energy from a meal, and many other things use energy conversions.

• Machines, such as a hair dryer, help harness energy and make that energy work for you.

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Why Energy Conversions Are Important, continued

31. Conversions Involving Electrical Energy Some common energy conversions that involve electrical energy are shown in the table below.

Chapter 9

Alarm clock electrical energy light and sound energy

Battery chemical energy electrical energy

Light bulb electrical energy light and thermal energy

Blender electrical energy kinetic and sound energy



Energy and Machines

• A machine can make work easier by changing the size or direction (or both) of the force needed to do the work. Some machines allow you to use less force over a greater distance to do the same amount of work.

• Machines as Energy Converters Some machines help you use energy by converting it into the form of energy that you need.

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Where Does the Energy Go?

• Friction is a force that oppose motion between two surfaces that are touching.

• For a roller coaster car to move, energy must be used to overcome the friction between the car’s wheels and the track.

• As a result, not all of the car’s potential energy changes into kinetic energy and not all of the car’s kinetic energy changes back into potential energy.

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Section 3 Conservation of EnergyChapter 9



Energy Is Conserved Within a Closed System, continued

• The image below shows energy conservation in a light bulb.

Chapter 9



No Conversion Without Thermal Energy

• Any time one form of energy is converted into another form, some of the original energy always gets converted into thermal energy.

• The thermal energy due to friction that results from energy conversions is not usually useful energy.

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No Conversion Without Thermal Energy, continued

• Perpetual Motion? No Way! A perpetual motion machine is a machine that would run forever without any additional energy.

• But perpetual motion machines are impossible because some waste thermal energy always results from energy conversions.

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No Conversion Without Thermal Energy, continued

• Making Conversions Efficient Some systems transform energy with less loss of heat than others do. Such systems are more efficient than others are.

• Improving the efficiency of machines is important because greater efficiency results in less waste. If less energy is wasted, less energy is needed to operate a machine.

Chapter 9


Use the terms below to complete the Concept Mapping on the next slide.

Concept Mapping

potential energypositionmechanical energymotion

kinetic energymassmachines

Energy and Energy ResourcesChapter 9


Energy and Energy ResourcesChapter 9

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