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How do pulleys help lift heavy loads?

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A diagram displays six types of simple machines with labeled illustrations: inclined plane, wedge, screw, lever, wheel and axle, and pulley, each shown with real-world examples like ramps, axes, screws, seesaws, door handles, and pulleys lifting objects. — machine Six simple machines for transforming energy into work.

A pulley is a simple machine consisting of a wheel with a grooved rim that carries a rope, cable, or chain. Pulleys help lift heavy loads by providing mechanical advantage, which is the force-amplifying effectiveness of the system.123

When used singly or in combination, pulleys allow a smaller input force to lift a much heavier weight. A common configuration is the block and tackle, which uses multiple pulleys and rope segments to distribute the load. In this setup, the force required to lift an object is reduced because the effort is spread across multiple rope links; for example, if a load is supported by four rope segments, the force required to lift it is theoretically reduced to one-fourth of its weight.124

While increasing the number of pulleys can create a higher mechanical advantage, the actual benefit is slightly reduced in practice due to friction within the system.43