lecture eighteen physics 100 fall 2012 conservation of energy
TRANSCRIPT
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Lecture Eighteen Physics 100 Fall 2012
Conservation of Energy
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No Lab Tomorrow. Lab WILL BE HELD Wednesday, Thursday
and Tuesday of next week. Second writing assignment due on
12/12/12 Exam 3 discussion
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An electric motor is a device that converts electrical energy into mechanical energy.
Electric motors use magnetic force to cause motion.
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Get “mechanical”
energy (motion) out
Put “electrical” energy (electricity)
in.
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Put “mechanical” energy in to
cause rotation
Get “electrical” energy (electricity)
out
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Amount of energy transfered
how long it took for the transferPower P
( ) (how long you use it) Amount of energy transferedPower x
Watt x hour or a kilowatt-hour is a unit of energy which can be converted into a Joule.
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P iV
Because V=iR
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Kinetic energy (or mechanical energy) is energy associated with motion.
KE=½ mv2 where m is the mass of an object and v is velocity or speed
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Put “mechanical” energy in to
cause rotation
Get “electrical” energy (electricity)
out
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Energy is not created or destroyed.
Rather, energy changes form (electrical to mechanical for example).
Or, is transferred from one object to another.
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Where did the energy come from to start with?
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Kinetic (mechanical) Electrical Heat Light from the sun and other objects Sound Potential (stored): Chemical bonds
including meat and plants, gravitational potential energy, springs, petroleum