Advertisement
EXPERIMENT 18
Compressed air
The air-filled balloon has potential
energy too. You can drive a paddle
wheel turbine with it.
1
8 x
23
17
3
Balloon
Power is work divided by time
Work is measured independent of the time it takes to do the work. If
you do the same amount of work in less time, then you exert more
power doing it — whether its raising your hand in school or biking.
When you calculate power, time
becomes a factor. Power is the
relationship of the work
performed to the time needed to
do it:
The unit of measure for power P
is the watt (W):
2
8
19
In addition to watts, kilowatts (1
kW = 1,000 W) and megawatts (1
mW = 1,000,000 W) are also used
as units of power. The engine of a
mid-sized car handles about 60
kW. A human can perform about
200 watts of physical work over
a long period of time, while a
cyclist with a bicycle can get to
1,500 watts fairly quickly.
CONSERVATION OF ENERGY
Not all of the potential energy of the
water is converted into hammer beats in
our gravity hammer experiment. Part of
it is used up by friction in the axle seats,
the pulley wheels, and the hammer
shaft. In this process, it is only lost as far
as the hammering is concerned. If you
add up the work from the friction and
the hammering, it equals the energy you
started with.
17
6
5
11
In other words,
energy law
applies:
Water, Air, and Energy
the conservation of
49
Advertisement
