Kinetic and Potential Energy

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Kinetic and Potential Energy
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After the Lesson

• You will be able to define and identify Kinetic
  and Potential energy.
• You will be able to give examples of the two
  forms of energy.
• You will be able to explain how one can transfer
  to the other.

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Definition of Energy
The ability or capacity to do work. Measured by
the capability of doing work potential energy
or the conversion of this capability to motion
kinetic energy.
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Types of Energy
Kinetic Energy
Potential Energy
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Forms of Energy
Chemical
Sound
Radiant
Electrical
Mechanical
Magnetic
Thermal
Nuclear
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Potential Energy

• Energy due to position or stored energy.

Potential energy is calculated by The objects
weight, multiplied by the earth's gravitational
pull (9.8 m/sec sq), multiplied by the distance
the object can fall.
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POTENTIAL ENERGY
Potential energy exists whenever an object which
has mass has a position within a force field. The
most everyday example of this is the position of
objects in the earth's gravitational field. The
potential energy of an object in this case is
given by the relation PE mgh  PE Energy
(in Joules) m mass (in kilograms) g
gravitational acceleration of the earth (9.8
m/sec2) h height above earth's surface (in
meters)
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Examples of Potential Energy
Stretching a rubber band.. -Stores energy
Water at the top of a waterfall.. -Stores
energy
YoYo in held in your hand.. -Stores energy
because of position
Drawing a Bow -Stores energy because of
position
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• When the position of an object is altered it,
  creates Potential Energy.
• A yo-yo on the table, doesnt have energy, but
  when picked up, it alters its position and now it
  has the ability (or potential) to do work.
• A bow doesnt have the capacity to do work,
  unless its held at an elevated position.

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Definition of Kinetic Energy
The energy of motion.
Kinetic energy is calculated by one half of the
objects mass, multiplied by the objects speed-
squared.
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KINETIC ENERGY
The greater the mass or velocity of a moving
object, the more kinetic energy it has.
Kinetic Energy Lab
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Examples of Kinetic Energy

• Shooting a rubber band.
• Water falling over the fall.
• A Yo-Yo in motion.
• Releasing the arrow from the bow.

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Potential Energy Converted to Kinetic Energy
When stored energy begins to move, the object now
transfers from potential energy into kinetic
energy.
Standing still
Running
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What happens when the cord is cut?
Potential energy is converted to kinetic energy!
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• Potential Energy-
• stored energy
• related to an objects height above the ground
• the higher something is, the more potential
  energy it has
• Kinetic Energy-
• energy of motion
• related to an objects velocity
• the faster something is traveling, the more
  kinetic energy it has

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Directions

• 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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The Ball
Kinetic Energy
Potential Energy
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Potential Energy
Kinetic Energy
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Potential Energy
Kinetic Energy
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Kinetic Energy
Potential Energy
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Kinetic Energy
Potential Energy
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Potential Energy
Kinetic Energy
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Potential Energy
Kinetic Energy
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Kinetic Energy
Potential Energy
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Kinetic Energy
Potential Energy
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• Conservation of energy says that the amount of
  energy the coaster has will always be constant.
  This means the potential energy of the car plus
  the kinetic energy of the car must always be the
  same. If the potential goes up, the kinetic must
  come down if the kinetic goes up, the potential
  must come down.

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The Hill Conservation of Energy
Why is the first hill of the roller coaster
always the highest?
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At the top of the first hill

• Kinetic Energy?
• The coasters velocity is zero . . .
• Kinetic energy 0
• Potential Energy?
• The coaster is very high . . .
• Potential energy high
• All of the coasters energy is in the form of
  potential energy.

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At the bottom of the hill

• Kinetic Energy?
• The coaster is moving at a high velocity.
• Kinetic energy high
• Potential Energy?
• The height of the coaster is zero . . .
• Potential energy 0
• By the time the coaster reaches the bottom of the
  hill, all potential energy has been transformed
  to kinetic energy.

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But why is the first hill highest?

• When the coaster reaches the bottom of the first
  hill, all its energy has been transformed from
  potential to kinetic energy.
• As it goes up the next hill, that kinetic energy
  must be transformed back into potential energy so
  the process can repeat.
• But dont forget friction the coaster is always
  losing energy to friction between the car and the
  tracks, so each time it goes up a hill it will
  have less kinetic energy to transform back into
  potential.

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• The first hill of a roller coaster always must be
  the highest, otherwise the coaster wont have
  enough energy to get up the other hills.