ENERGY

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ENERGY
THE ABILITY TO CAUSE CHANGE
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Types of Energy
mechanical energy
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• types of energy
• Thermal energy - due to temperature (recall that
  this comes from the motion of molecules, so it is
  really kinetic energy)
• Heat energy -transfer of thermal energy
• Chemical Potential Energy - stored in chemical
  bonds
• Nuclear energy - stored in the nuclei of an atom
• Electrical energy - EM interactions
• Radiant energy -carried by EM waves

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Energy
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CLIP

• Energy is the capacity (ability) to do work. 
• Kinetic Energy Associated with an object in
  motion
• Potential Energy Present in an object that has
  the potential to move because of its position

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Kinetic Energy
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• Motion
• KE of an object depends upon two variables
• the mass (m) of the object
• the speed (v) of the object.

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Calculating Kinetic Energy

• A formula to find the kinetic energy of any body
  based on its velocity.

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Potential Energy
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• An object can store energy as the result of its
  position.

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Forms of potential energy
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Gravitational Elastic Chemical
-position above the Earths surface
-stored in something stretchy
-chemical reaction
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Gravitational Potential Energy
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• GPE is the energy stored in an object as the
  result of its vertical position (i.e., height).
• Amt. of GPE is dependent on two variables
• the mass
• the height

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Calculating Gravitational Potential Energy
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GPE mgh
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Elastic Potential
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• Elastic PE is the energy stored in elastic
  materials as the result of their stretching or
  compressing.

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Conservation of Energy
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Conservation of Energy
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• Energy cannot be created or destroyedonly
  changed from one form to another.
• The total energy of an isolated system remains
  constant (isolated systems have no external
  forces and no mass changes)

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ENERGY BEFORE ENERGY AFTER Energy can be
changed from one form to another, but it does not
disappear.
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Mechanical Energy
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• The motion of some objects contain a combination
  of only kinetic and potential energies.
• ME is the sum of the KE and forms PE associated
  with a system
• Therefore, ME KE PE

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Conservation of Energy
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TOTAL ENERGY OF THE SYSTEM REMAINS THE SAME
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Conservation of Energy
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TOTAL ENERGY OF THE SYSTEM REMAINS THE SAME
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Conservation of Mechanical Energy
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• Therefore,
• MEi MEf
• KEi PEi KEf PEf

• ½ mvi2 mghi ½ mvf2 mghf

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Conservation of Mechanical Energy
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• Conservation of ME only hold true when the only
  energies of the system are KE and PE.
• Therefore, in the presence of friction energy is
  transformed to other types of energies.

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Energy Conversion
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• When one type of energy is changed or transformed
  into another type of energy

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Examples
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Lighting a Match
Steam Engine
Battery
Can you think of More? Create a graphic organizer
to illustrate energy conversions. draw a picture
to represent four different energy conversion you
may encounter in everyday life. Be sure to
explain what type of energy it starts with and
what type of energy it ends with.
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Energy Conversion
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• clip

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What about a falling object?
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• What happens when it hits the ground?
• Where did the energy all go?

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Energy Conversions of a dropped object
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• As it is falling and when the object hits the
  ground the energy is converted into other types
  of energy such as

• sound energy (waves), Light Energy (sparks),
  thermal energy due to friction (heat) in the
  ground and air, vibrations in the earth (energy
  waves.)

• If the object bounces, some energy is converted
  momentarily into elastic potential energy.

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If Robin Hood had been Written by an
Engineer....    And Robin didst slowly and with
great determination put potential energy equal to
the work of his muscles into an elastic storage
device.                                         
                                     And
therewith Robin the Bold and Valiant didst
convert this stored energy most quickly,
efficiently, and accurately into the velocity of
a sturdy and pointed dart (oft called arrow) such
that almost all of its former potential energy
didst become kinetic. Then this speedy dart didst
split an arrow (oft called dart) already buried
in most distant target, having been previously
hurled there at an equally great speed by a
similar conversion of stored energy.
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EOCT Questions
Which statement about energy is true? A Energy
can be increased in a closed system. B
Energy cannot be conserved. C Energy can be
decreased in a closed system. D Energy cannot
be created nor destroyed.
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