Ch.9, Sec.3

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Ch.9, Sec.3 Conservation of Energy

• Where Does the Energy Go?

• friction a force that opposes motion between
  two surfaces that are in contact

• on a roller coaster, not all potential energy is
  converted into kinetic energy because of friction!

• kinetic energy can be converted into thermal
  energy instead of going back to potential

• Energy Is Conserved Within a Closed System

• a closed system is a group of objects that
  transfer energy only to each other

• energy is always conserved and never lost!

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Ch.9, Sec.3 Conservation of Energy

• law of conservation of energy this law states
  that energy cannot be created or destroyed but
  can change from one form to another

• the total amount of energy in a closed system is
  always the same

• energy is conserved in all cases no exception
  has been found!

• No Conversion Without Thermal Energy

• thermal energy due to friction is NOT useful (it
  cannot be used for work)

• example car (wasted thermal energy leaves the
  radiator the exhaust)

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Ch.9, Sec.3 Conservation of Energy

• perpetual motion is NOT possible because a
  constant energy supply is needed

• energy efficiency is a comparison of the amount
  of energy before a comparison with the amount of
  useful energy after a conversion