pulley
A pulley is a simple but clever mechanical device used in many different industries and in a variety of ways. At its heart a pulley is a device used to change the direction of an applied force and make it easier to lift or move heavy objects. This machine, usually composed of a wheel, rope or belt, and support system taps the energy stored within leverage. The various designs of the structural elements are:fixed, movable, and compound pulleys appropriate to intended task with corresponding technological features. Pulleys are commonly used in everything from construction cranes to window blinds, illustrating their extensive use in everyday activities as well as complicated industrial processes.