Work has a specific definition in physics. Work is done anytime a force is applied through a distance.

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Work has a specific definition in physics. Work
is done anytime a force is applied through a
distance.
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W Fd The unit is the newtonmeter, or joule.
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A component of the force must be in the direction
of the displacement.Only this component is used
when calculating the work.
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Example How much work is done on a vacuum
cleaner pulled 3.0 m by a force of 50.0 N at an
angle of 30.0 above the horizontal?
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Work can be positive or negative depending on
whether the force is in the same direction as
displacement or in the opposite direction.
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For example If you push a box, the work is
positive but the work the friction does is
negative.
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Kinetic energy is the energy of motion. KE 1/2
mv2
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KE is a scalar and the unit is the joule.
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Example A 7.00 kg bowling ball moves at 3.00
m/s. How much kinetic energy does the bowling
ball have? How fast must a 2.45 g table tennis
ball move in order to have the same kinetic
energy as the bowling ball? Is this reasonable?
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The net work done by a net force acting on an
object is equal to the change in the kinetic
energy of the object.
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This is called the work-kinetic energy
theorem W ?KE
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Example 25 joules of work is done to a 2 kg
ball. If the ball is not moving initially, how
fast is it moving after the work is done?
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Example A person kicks a 10.0 kg sled, giving it
an initial speed of 2.2 m/s. How far does the
sled move if the coefficient of kinetic friction
between the sled and the ice is 0.10?
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Potential Energy is stored energy, energy of
possible motion, energy of position.
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One type of potential energy is gravitational
potential energy. PE mgh
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Example A 5 kg bunch of bananas is at the top of
a 6 meter palm tree. What is the gravitational
potential energy of the bunch of bananas?
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PE mgh is just W Fd.
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The unit of potential energy is the joule. (The
unit of all types of energy and work is the
joule.)It is always measured relative to a zero
level.
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Another type of potential energy is Elastic
Potential Energy.This energy is stored in a
compressed or stretched object.
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The formula for elastic potential energy is
PEelastic 1/2 kx2The symbol k is the spring
constant, x is the distance compressed or
stretched.
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The spring constant is a measure of the force
needed to stretch or compress a spring. It is
measured in newtons per meter, N/m.
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Example How much energy is stored in a spring
with a spring constant of 10 N/m if it is
stretched 2 meters?
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Example A 70.0 kg stuntman is attached to a
bungee cord with an unstretched length of 15.0 m.
He jumps from a height of 50.0 m. When he stops,
the cord has stretched to 44. 0 m. If k for the
cord is 71.8 N/m, what is the total PE relative
to the ground when the man stops falling?
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