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# Power - interval is The instantaneous power can be written...

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Power In every day life, the amount of work an apparatus can do is not always important. In general it is more important to know the time within which a certain amount of work can be done. For example: the explosive effect of dynamite is based on its capability to release large amounts of energy in a very short time. The same amount of work could have been done using a small space heater (and having it run for a long time) but the space heater would cause no explosion. The quantity of interest is power. The power tells us something about the rate of doing work. If an amount of work W is carried out in a time interval [Delta]t, the average power for this time-
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Unformatted text preview: interval is The instantaneous power can be written as The SI unit of power is J/s or W (Watt). For example, our usage of electricity is always expressed in units of kilowatt . hour. This is equivalent to 7.3.1. kW . h = (10 3 W) (3600 s) = 3.6 x 10 6 J = 3.6 MJ We can also express the power delivered to a body in terms of the force that acts on the body and its velocity. Thus for a particle moving in one dimension we obtain In the more general case of motion in 3 dimensions the power P can be expressed as...
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