With a simple pulley the force you must exert is equal to the weight of the load. With a compound pulley—two or more pulleys combined together—you can reduce the force required to lift the load.

EXPLANATION: A pulley is one of the six simple machines. Single pulleys were part of simple cranes invented more than 3,000 years ago. A pulley consists of a wheel that is free to turn its center.

Find out how simple machines makes work easier on this Science Trek. Simple machines include the lever, the inclined plane, the wedge, the pulley, the wheel and axle, and the screw. Combine these ...