pulley
close In mechanics, a typical pulley is a round wheel that can rotate around a central axis. There is a groove on the circumference surface of the round pulley. Wrap the rope around the groove and pull either end of the rope with force. The friction between the rope and the round pulley will cause the round pulley to rotate around the central axis. The pulley is actually a deformed and rotatable lever. The main functions of the pulley are to pull the load, change the direction of force application, transmit power, etc. The machinery composed of multiple pulleys is called "pulley block", or "compound pulley". The pulley block has greater mechanical benefits and can pull heavier loads. Pulley can also be a component of chain drive or belt drive to transmit power from one rotating shaft to another. Pulleys can be divided into "fixed pulley" and "movable pulley" according to whether the central axis of the pulley moves; The central axis of the fixed pulley is fixed, while the central axis of the movable pulley can be moved. Each has its own advantages and disadvantages. The fixed pulley and the movable pulley can be assembled together to form a pulley block, which not only saves labor but also can change the direction of force. Pulleys appear in the form of knowledge points in junior high school physics textbooks, which require answers to questions such as the direction of force, the distance of rope end movement, and the work done.