Unit 3 Lesson 2 Conservation of Energy Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 3 Lesson 2 Conservation of Energy

Copyright © Houghton Mifflin Harcourt Publishing Company

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What are some forms of energy?

1. Mechanical energy is the sum of an object’s kinetic energy and potential energy.• Kinetic – energy of motion• Potential – energy of position

2. Sound energy results from the vibration of particles. This is why sound cannot travel through empty space.



3. Electromagnetic energy is transmitted in the form of electromagnetic waves (EM waves).

• EM waves are produced by the vibration of electrically charged particles.

• Electromagnetic waves can travel through empty space.




4. Chemical energy is the energy stored in chemical bonds that hold chemical compounds together.

5. Thermal energy is the energy an object has due to the motion of its molecules.

• The faster the molecules move, the more thermal energy the object has.

• Heat is the transfer of thermal energy.




6. Nuclear energy comes from the nucleus of an atom.

• When an atom’s nucleus breaks apart, or when the nuclei of two atoms join together, energy is released.



Transformers


What is an energy transformation?

• An energy transformation takes place when energy changes from one form into another form.

• Any form of energy can change into any other form of energy.

• Often one form of energy can change into two or more other forms.


What is an energy transformation?

• In a flashlight, chemical energy is transformed into electrical energy.

• The electrical energy is then transformed into light and thermal energy.



How does mechanical energy transform?• Although mechanical energy can be transformed

into another form of energy, transformations between kinetic and potential energy can also take place.

• However, regardless of the changes in kinetic and potential energy, the total amount of mechanical energy remains the same.



Energy In = Energy Out


What is conservation of energy?

• The law of conservation of energy states that energy cannot be created or destroyed; it can only change forms.

• A group of objects that transfers energy only to one another is called a closed system.

• In a closed system, all the energy is conserved.


How is energy conserved?

• Energy is measured in Joules. • The law of conservation of energy means that the

total number of joules of energy in a closed system always remains the same.

• When analyzing how energy is conserved in a closed system, it is important to always consider all objects in the system.



Efficiency Expert!


How is efficiency measured?

• When energy is transformed from one form to another form, not all of it is turned into useful energy.

• Usually, some energy is also transformed into thermal energy.

• Efficiency is the ratio of useful output energy to input energy.


How is efficiency measured?

• Energy efficiency is highly desirable because it means as much energy as possible is converted to useful forms.

• Efficiency is calculated by dividing energy out by energy in and then multiplying by 100 percent.

• If less energy is wasted, then less energy is needed to operate a machine.



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Unit 3 Lesson 2 Conservation of Energy Copyright © Houghton Mifflin Harcourt Publishing Company