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Power!power1.htm;
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Joule's Experiment!joule's experiment.htm;
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Power
Two persons lift 4 boxes each through a height of 5
m. This means that they do the same amount of work. However, one
person is stronger and powerful and he lifts all of his box in
one go. Other person is rather less strong and less powerful, lifts her
box
two at
a time. We use the word powerful to describe someone who can do
the work quickly. Power is the rate of doing work or converting
energy.
Power = Work done or energy converted/Time taken
From the equation above you can see that power
is measured in 1 J/s. But we give power its own unit called the
watt. 1 watt is equal to the arte of working of 1 J/s. Power
changes can be very large; Then we use the units of K W
(Kilowatt or 1000 W) and MW (MEGAWATT OR 106 w).
Unit of power :
The power was earlier measured in a unit called
HORSE POWER.
One horse power = 746 watt
One kilowatt of power supplied for one hour
amounts to one Kilowatt-hour of energy. The Kilowatt-hour is
used as a commercial unit energy.
One unit = One Kilo-watt hour
= 3600000 Joules.
Body Power :
A girl measured its personnel power output by
running up a flight of steps. She takes 8.4 s to run up a flight
of steps. Her mass is 14 kg. What power does she develop. She
has done some work to lift her weight of 140 N through a height
of 6m.
