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ENERGY

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**Energy is used everyday… Can you think of any examples?**

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**Energy can take many forms**

sun power lines gas, food energy that comes from the particles that make up matter fission (reactor) radiant electrical chemical thermal nuclear

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**Traditionally, energy is defined as…**

the ability to do work or to cause something to move. However, energy involves change, therefore a better definition is: ENERGY = the ability to cause change. The basic unit of energy is the Joule (J). The equivalent units are : N*m

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Energy Kinetic Potential

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**Kinetic Energy Kinetic energy is energy in the form of motion.**

The amount of kinetic energy in a moving object depends on its mass and velocity The formula for kinetic energy is : KE = ½ mv2

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**KE = 1/2 mv2 Kinetic Energy energy of motion**

All moving objects that have mass have kinetic energy. KE = 1/2 mv2 m - mass of the object in kg v - speed of the object in m/s KE - the kinetic energy in J

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**Which of each pair has more kinetic energy?**

a bus traveling at 65 mph? a bus traveling at 65 mph car traveling at 65 mph bus traveling at 40 mph

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**Potential Energy Potential Energy is stored energy.**

The amount of potential energy in a sample of matter depends on its position or condition. Potential energy due to height above Earth’s surface is called gravitational potential energy. Formula: PE (due to gravity) = mgh 9.8m/s2

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**PEg = mgh Potential Energy energy of position or condition**

gravitational potential energy PEg = mgh m - mass of object in kg g - acceleration of gravity in m/s2 h - height of object, in m, from some arbitrary reference point PE – gravitational potential energy in J

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**Circle which of each pair has more potential energy:**

boy sitting in a tree 12 ft. in the air. squirrel sitting in a tree 30 feet in the air squirrel sitting in a tree 12 ft. in the air squirrel sitting in a tree 12 ft in the air.

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**Click on your answer to see if you are correct.**

Directions Click your mouse to begin. Decide whether each slide is an example of potential or kinetic energy. Click on your answer to see if you are correct. Whenever you see this picture, you will need to write the answer in your journal.

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The Ball Kinetic Energy Potential Energy

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Kinetic Energy Potential Energy

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Kinetic Energy Potential Energy

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Kinetic Energy Potential Energy

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Kinetic Energy Potential Energy

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**Conservation of Energy**

The law of conservation of energy states that energy may change form, but it cannot be created or destroyed under ordinary conditions. Mechanical Energy is the total amount of potential and kinetic energy in a system. The amount of kinetic and potential energy in a moving swing is always changing, whereas the amount of mechanical energy is constant.

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**continued… Let’s look at the case of a bouncing ball.**

Energy changes from potential energy at the top of the bounce to kinetic energy when it hits the floor , and back to potential energy as it goes back up. During this time, the mechanical energy of the ball stays constant.

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**5. Fill in the diagram of a bouncing ball with the correct response below.**

greatest potential energy, no kinetic energy kinetic energy decreasing, potential energy increasing kinetic energy increasing, potential energy decreasing greatest kinetic energy, no potential energy greatest kinetic energy, no potential energy

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**Because gravity will slow the ball down .**

6a. The ball in the previous diagram will eventually stop bouncing. Why? Because gravity will slow the ball down . 6b. As the ball stops bouncing, is energy lost? Explain. No, because the kinetic energy eventually changes to potential energy, but energy is not lost.

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**7b. Where does it have the most kinetic energy?**

7a. In this picture, where does the roller coaster have the most potential energy? At the top because it has an instantaneous speed of 0 m/s. 7b. Where does it have the most kinetic energy? At the bottom because it’s where it is going the fastest.

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References faculty.physics.tamu.edu/ford/PowerPoints/WorkEnergyPower.ppt

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Energy in Motion 8SCIENCE. How is energy related to motion? Energy of matter in motion is called kinetic energy – Energy is the ability to cause a change.

Energy in Motion 8SCIENCE. How is energy related to motion? Energy of matter in motion is called kinetic energy – Energy is the ability to cause a change.

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