Subsubsection Power
Power is the rate of doing work. The amount of work done has nothing at all to do with how long it takes to do it. When you lift a weight of 1 pound through a distance of 1 foot, you have done 1 foot-pound of work, regardless of whether you do it in half a second or half an hour. A device which can do a lot of work quickly is powerful. The common unit of measurement for power is the horsepower (hp). By definition, 1 horsepower is equal to 33,000 foot-pounds of work per minute or 550 foot-pounds of work per second. Thus a machine that is capable of doing 550 foot-pounds of work per second is said to be a 1-horsepower machine. (As you can see, your horsepower rating would not be very impressive if you did 1 foot-pound of work in half an hour. Figure it out. It works out to be just a little more than one-millionth of a horsepower.)
