Pulleys can change the direction of an applied force.

A pulley is a device that aids in moving or lifting objects. Like most wheels, pulley wheels spin or rotate on an axis. The outer edge of a pulley wheel features a groove. Nested in this groove is a rope, belt, or a cable.

The man in the image is pulling downward on a bar that is attached to a cable. If you trace the cable’s path through the machine, you’ll notice that it passes through the pulley wheels, and its opposite end is connected to the weights in the bottom-left corner.

Parts of a Pulley System

There are three important things to consider in this scenario: the effort (the force the man is applying to the bar), the load (the weight that’s being lifted), and the fulcrum (the pivot point of the pulley – there are several in this case).

Direction of Force

Notice that the pulleys change the direction of the applied force. Although the man is pulling downward, the weights are moving upward.

Types of Pulley Systems

There are three basic types of pulley systems: fixed pulley, moveable pulley, and block and tackle. The three types of pulleys are classified based on the position and number of pulley wheels.