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Leverage
From Wikipedia, the free encyclopedia
Leverage is a factor by which lever multiplies a force - it is therefore related to mechanical advantage. The useful work done is the energy applied, which is force times distance. Therefore a small force applied over a long distance is the same amount of work as a large force applied over a small distance. The trick is converting the one into the other. The requisite mathematics was developed in the third century B.C. by Archimedes.
The simplest device for creating leverage is the lever. A lever is a stick which rests on a fulcrum near one end. When you push the long end of the stick down a long ways, the short end moves a small distance up with great force. With this device a man can easily lift several times his own weight.
Other common devices that achieve leverage include the wrench, various pulley arrangements, a jack, and hydraulic brakes.