Pulley

A pulley is a wheel with a grooved rim that guides a rope or cable. It can redirect a pull or, in a system, reduce the force needed to lift a load.

Mechanical advantage: The ratio of a machine’s output force to its input force. Supporting a load with multiple rope segments can increase this ratio.
Lever: A rigid bar that turns around a fulcrum to transmit or multiply force. Like a pulley, it is a simple machine that can trade force for distance.
Crane: A machine that lifts and moves heavy loads using ropes, cables, or hydraulic systems. Cranes use pulley arrangements to lift loads and route hoist cables.
Archimedes: An ancient Greek mathematician and engineer known for work on mechanics and hydrostatics. Ancient accounts associate him with demonstrations of compound pulley systems.
Fixed pulley: A pulley mounted so its axle stays in place during use. It redirects a pull without ideally reducing the force needed to lift a load.
Wheel and axle: A simple machine consisting of a wheel fixed to a smaller axle that turn together. A pulley is a grooved wheel rotating around an axle.
Elevator: A platform or compartment that moves people or goods between levels in a building. Many elevators use sheaves to guide suspension and hoisting cables.
Vitruvius: A Roman architect and engineer whose treatise De architectura describes ancient building practices and machines. His work records Roman knowledge of hoists and pulley mechanisms.
Movable pulley: A pulley whose axle moves with the load it supports. The load is shared by rope segments, reducing the required input force.
Tension: The pulling force transmitted through a taut rope, cable, or other flexible connector. Tension carries the applied pull through the pulley system to the load.

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