Pulley

A pulley is a wheel that carries a flexible rope, cord, cable, chain, or belt on its rim. Pulleys are used individually or in combination to transmit power and motion. Pulleys with grooved edges are called sheaves. In belt drives, pulleys are attached to shafts at their axles, and power is transmitted between the shafts by endless belts running over the pulleys. One or more independently rotating pulleys can be used to gain a mechanical advantage, particularly when lifting weights. Pulleys are assembled to form a block and tackle in order to provide a mechanical advantage to apply large forces. Pulleys are also assembled as part of belt and chain drives in order to transmit power from one rotating shaft to another