Energy and Energy Resources

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Chapter 9

• Energy and Energy Resources

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Terms to Learn

• Energy the ability to do work.
• Kinetic Energy the energy of motion(KE)
• depends on speed and mass
• Potential Energy the energy of position or
  shape.(PE)

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ENERGY

• Energy is the ability to do work work is the
  transfer of energy.
• Both energy and work are expressed in Joules (J).

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ENERGY

• The tennis player is doing work on her racket
  because she has energy
• When she does work on the racket, the racket
  gains the ability to do work on the ball.

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ENERGY

• Energy is transferred from the tennis player to
  the racket.
• When the racket does work on the ball, the ball
  gains the ability to do work on something else.
  Energy is transferred from the racket to the
  ball.

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Forms of Energy

• Thermal energy
• Chemical energy
• Electrical energy
• Sound energy
• Light energy
• Nuclear energy

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FORMS OF ENERGY

• Thermal energy the total energy of the
  particles that make up an object.
• The higher the temperature, the faster particles
  move and the more K.E. they have
• Thermal energy also depends on the number of
  particles there are in a substance.
• See Figure 5 on p. 244

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FORMS OF ENERGY

1. Chemical energy the energy of a compound that
   changes as its atoms are rearranged to form new
   compounds. Chemical energy is a form of
   potential energy.

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Electrical Energy

• Is the energy of moving electrons
• Both kinetic and potential energy

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Sound Energy

• Is caused by an objects vibrations
• It is a form of potential and kinetic energy

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Light Energy

• Is produced by the vibrations of electrically
  charged particles
• Kinetic energy

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Nuclear Energy

• The energy associated with changes in the nucleus
  of an atom Nuclear power plants use uranium, a
  radioactive element, to create electricity.
• Potential Energy

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Kinetic Energy

• Kinetic energymv2
• 2
• mmass (kg)
• vvelocity (m/s)
• KEJoules
• As the roller coaster descends its velocity
  increases causing the roller coaster to gain
  kinetic energy.

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TYPES OF ENERGY

• Kinetic Energy (K.E.)
• Depends on
• Speed and
• Mass
• Speed has more of an effect on Kinetic Energy
  than mass because speed is squared in the
  equation.

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POTENTIAL ENERGY

• Also known as P.E. or G.P.E.
• Energy of position or shape
• Gravitational potential energy depends on
• Weight and
• Height (distance above Earths surface)

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POTENTIAL ENERGY

• The stored potential energy of the bow and string
  allows them to do work on the arrow when the
  string is released

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POTENTIAL ENERGY

• Equation for GPE
• GPE weight ? height
• or
• GPE mass ? g ? height
• Weight mass ? g

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Potential Energy

• GPE is measured in Joules (J)
• mass is measured in kg
• height is measured in meters (m)
• g is acceleration due to gravity and is a
  constant number- 9.8 m/s2

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Energy Partners
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Terms to Learn

• Mechanical Energy is the total energy of motion
  and position of an object. It can be all
  potential energy, all kinetic energy, or some of
  both.
• Mechanical energy potential energy kinetic
  energy
• MEPEKE

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Mechanical Energy

• When potential energy increases (or
  decreases), kinetic energy has to decrease (or
  increase) in order for mechanical energy to
  remain constant.

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Conservation of Energy
Chapter 9
Energy Is Conserved Within a Closed System

• A closed system is a group of objects that
  transfer energy only to each other.
• The Law of Conservation of Energy states that
  energy cannot be created or destroyed.
• Energy can be converted from one form to
  another. But all of the different forms of energy
  in a system always add up to the same total
  amount of energy.

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No Conversion Without Thermal Energy

• During energy conversions some of the original
  energy is always converted into thermal energy
• This is due to friction
• This energy is not always useful