energy notes

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ENERGY
Notes and Key Concepts
Work
 An
object’s motion is related to both
force and how the force acts.
 The quantity force X time = impulse
 The quantity force X distance = work
WORK
Two factors are
considered when
work is done
1. The application of
a force
2. The movement of
something by that
force


The work done on an
object by an applied
force is the product
of the force and the
distance through
which the object
moved
Work=force x
distance
W=Fd
POWER
 Power
is the rate at which work is done
 Power=work done/time interval
 The unit of power is the joule per second, also
known as the watt
 One watt (W) of power is expended when one joule
of work is done in one second
 1 Kilowatt (kW)= 100 watts
 1 megawatt (MW) = one million watts
Metric System vs. United States
 In
the metric system, automobiles are
rated in kilowatts
 In the U.S, we rate engines in units of
horsepower and electricity in kilowatts
 One horsepower (hp, is the same as 0.75
kW, so an engine rated at 134 hp is a 100kW engine
Mechanical Energy
Potential
Potential energy is
stored and held in
readiness (a spring or
stretched rubber
band)
Examples: fossil fuels,
electric batteries,
and food
Gravitational
potential energy=
weight x height
PE=mgh





 Kinetic
 Kinetic
energy is
energy of motion
 It depends on mass
and speed of an
object
 Kinetic energy = ½
mass x speed2
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