Potential and Kinetic Energy

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Potential and Kinetic Energy
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What is Energy???
The ability of an object To do work
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Two Main Types of Energy
All Energy
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What is Potential Energy?

• Energy that is stored and waiting to be used later

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What is Gravitational Potential Energy?

• Potential energy due to an objects position
• P.E. mass x
• height x gravity

Dont look down, Rover! Good boy!
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ARRGGGG!! NO TRIANGLE
Gravity ?
PE
Height
Mass
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Find the Potential energy of a 20 kg bag of dog
food elevated 5 meters above the ground on a
shelf.
Mass 20 kg
PE mx g x h
Height 5 m
PE 20 kg x 9.8 m/s2 x 5 m
PE 980 J
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Find the potential energy of a 65 kg climber on
top of Mt. Everest ( 8800 m high).
Mass 65 kg
PE mx g x h
Height 8800 m
PE 65 kg x 9.8 m/s2 x 8800 m
PE 5 605 600 J
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What is Elastic Potential Energy?

• Potential energy due compression or expansion of
  an elastic object.

Notice the ball compressing and expanding
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What is Chemical Potential Energy?

• Potential energy stored within the chemical bonds
  of an object

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What is Kinetic Energy?

• Energy an object has due to its motion
• K.E. .5(mass x speed2)

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Kinetic Energy
Depends on
Mass
and
Speed
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KE ½ mass x velocity2 KE ½ M X V2
What is the kinetic energy of a 44kg cheetah
running at 31 m/s?
KE ½ M x V2
Mass 44 kg
Speed 31 m/s
KE .5 x 44 kg x (31 m/s)2
KE 21 142 J
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KE ½ mass x velocity2 KE ½ M X V2
What is the kinetic energy of a 400kg elevator
descending at a rate of 5 m/s?
KE ½ M x V2
Mass 400 kg
KE 400 kg x (5 m/s)2
Speed 5 m/s
KE 5 000 J