Energy

1
Energy
2
What is energy?

• Every change that occurs big or small requires
  energy.
• When something is able to change its environment
  or itself, it has energy.
• Energy is the ability to cause change.

3
Examples

• What are some examples of having or using energy?
• A moving baseball
• Combing your hair
• Walking up the stairs

4
Different Forms

• There are different forms of energy.
• When you turn on a light, the room gets brighter.
• When you turn on your stereo, you hear sound.

5
Think of money

• If you had 100, you can keep it
• In your wallet
• In a bank account
• In travelers checks
• In gold and silver coins
• The same is true for energy!! It can be found in
  different forms.

6
Kinetic Energy

• Kinetic energy is energy in the form of motion.
• Wheels spinning
• A sprinting runner
• A train moving

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Kinetic Energy

• Kinetic energy depends on two quantities
• The mass of the moving object
• The objects velocity

8
Kinetic Energy

• The more mass an object has, the more kinetic
  energy it has.
• The greater an objects velocity is, the more
  kinetic energy it has.

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Kinetic Energy

• Which one has the most kinetic energy?

Velocity 5 m/s Mass 500 kg
Velocity 20 m/s Mass 500 kg
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Kinetic Energy

• Kinetic energy is measured in joules (J)
• We use the following equation to calculate how
  much kinetic energy an object has
• Kinetic Energy ½ (mass) x (velocity)2
• KE ½ m v2
• KE (joules) ½ m (kg) x v2 (m2/s2)

11
Racecar

• If a racecar with a mass of 800kg is traveling at
  35 m/s how much kinetic energy does the car
  have?
• KE ½ mv2
• KE ½ (800kg) x (35 m/s)2
• KE 490000 J or 490 kJ

12
Potential Energy (PE)

• Even motionless objects can have energy the
  energy is stored in the object.
• An apple hanging in a tree has potential energy
  because it has the ability to cause change, to
  fall to the ground.
• Stored energy due to a position is called
  potential energy (PE).

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Elastic Potential Energy

• Elastic potential energy is energy stored by
  something that can stretch or compress such as a
  rubber band or a spring.

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Chemical Potential Energy

• Energy stored in chemical bonds is called
  chemical potential energy.
• Chemical energy is stored in bonds that hold a
  molecule together and are released when the bond
  is broken.

15
Gravitational Potential Energy

• Gravitational potential energy (GPE) is stored by
  objects that are above the Earths surface.
• The amount of GPE depends on
• The mass of the object
• The acceleration due to gravity
• The height above the ground

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Gravitational Potential Energy

• To calculate the GPE of an object, we use the
  following equation
• GPE mass x gravity x height
• GPE mgh
• GPE (J) m (kg) x g (m/s2) x h (m)

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Changing GPE

• The GPE of an object can be changed by changing
  the height of the object.
• When the height of the object is increased, the
  gravitational potential energy increases!!