What Is A Pulley

Pulley is a simple machine used to lift heavy objects and save labor.
A pulley is a small wheel with grooves around it that can rotate around an axis. A simple machine that can rotate around a central axis, consisting of a grooved disc that can rotate around a central axis and a flexible cable (rope, tape, steel cable, chain, etc.) that spans the disc, is called a pulley.
In mechanics, a typical pulley is a round wheel that can rotate around a central axis. There is a groove on the circumferential surface of the wheel. Wrap the rope around the groove and pull either end of the rope hard. The friction between the rope and the wheel will cause the wheel to rotate around the central axis. Pulleys are actually deformed, rotating levers. The main function of the pulley is to pull the load, change the direction of force, transmit power, etc. A machine composed of multiple pulleys is called a "pulley block" or a "compound pulley". The pulley block has greater mechanical benefits and can pull heavier loads. Pulleys can also be components of a chain or belt drive, transmitting power from one rotating shaft to another.
Depending on whether the central axis of the pulley moves, the pulleys can be divided into "fixed pulleys" and "movable pulleys"; the central axis of the fixed pulley is fixed, while the central axis of the movable pulley can move, each with its own advantages and disadvantages. The fixed pulley and the movable pulley are assembled together to form a pulley block. The pulley block not only saves labor but can also change the direction of the force.
Pulleys appear as knowledge points in junior high school physics textbooks, requiring answers to questions such as the direction of the force, the distance the rope end moves, and the work performed.