Leverage is a factor by which a 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 were developed in the third century B.C. by Archimedes. The simplest device for creating leverage is the lever. A lever can be a stick which rests on a fulcrum near one end. When the long end of the stick is pushed down, the short end moves a small distance up with great force. With this device a person can easily lift several times their own weight, but cannot lift it very far in one go. Other common devices that achieve leverage include the wrench, various pulley arrangements, a jack, and hydraulic brake. Not all levers provide leverage. Horse tack includes several simple leverage devices.