What Is a Pulley?

Pulleys are all around you! They are at work on bikes, flagpoles, window shades, sailboats, and some elevators. Pulleys are at work in buildings, in factories, and on farms, too. These pulleys make it possible to raise and lower heavy loads with ease.

A pulley is one of six common simple machines, or objects that do work. The other simple machines are the lever, the inclined plane, the wheel and axle, the screw, and the wedge. Compound machines, also called complex machines, are machines made up of many smaller simple machines. Tractors, cranes, and bulldozers are all compound machines.