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14.1 Work and Power
What is Work?


Work is the product of force and
distance.
Work is done when a force acts on
an object in the direction the object
moves.
Work Requires Motion


For a force to do
work on an object,
some of the force
must act in the
same direction as
the object moves.
If there is no
movement, no
work is done.
Work Depends on Direction

Any part of a force that does not act in
the direction of motion does no work on
an object.
Calculating Work
SI Units of Work


When using SI units in the work
formula, the force is in newtons,
and distance is in meters.
The product of force and distance
results in the units of newtonmeters, also know as joules.
Using the Work Formula
Work = Force x Distance
Work = 1600 N x 2.0 m
Work = 3200 N*m = 3200 J
What is Power?
Power is the rate of doing work


Doing work at a faster rate requires
more power.
To increase power, you can increase
the amount of work don in a given
time, or you can do a given amount
of work in less time.
You know what this
needs: More Power!
Calculating Power
SI Units of Power


When using SI units in the power
formula, work is in joule (J) and
time is in seconds (s).
The SI unit of power is the watt
(W), which is equal to one joule per
second.
Watt (W)


A 40 watt light bulb requires 40
joules each second that it is lit.
40 watts of power is also
approximately equal to lifting your
textbook a height of 1 meter in
.5 seconds.
Using the Power Formula
Power = Work = Force x Distance
Time
Time
Power = 72 N x 1.0 m
2.0 s
= 36 J/s = 36 W
Horsepower

One horsepower (hp) is equal to about
746 watts.
SI Units
Time
Seconds (s)
Distance
Meters (m)
Mass
Kilogram (kg)
Velocity/Speed m/s
Acceleration
m/s2
Force
Newtons (N)
Work
Joules (J)
Power
Watts (W)