Pulley

machines · engineering · lifting

Wheel with a groove. A pulley is a wheel on an axle with a rope or belt running over it. The groove keeps the rope from slipping off.

Easier lifting. By using more than one pulley together, you can lift a heavy load with much less force. The trick is that you pull a longer length of rope instead.

Changing direction. A single pulley lets you pull down on a rope to lift something up, which is way more comfortable than pulling upward.

Everywhere you look. Pulleys help raise flags up poles, lift sails on boats, run cranes, and even move elevators.

A simple machine. Pulleys are one of the classic 'simple machines,' along with levers, wheels, and ramps, that humans have used for thousands of years.