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.

Explore the clever mechanics behind pulleys in Jiwi's Machines Episode 2. Discover how simple systems create powerful movements in this exciting Science Extra feature.

Students started weeks ago by learning about the six simple machines — the inclined plane, lever, wedge, wheel and axle, pulley and screw.

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 ...

Inside-out constructions made from folded steel and industrial parts, including the Counterweight Table, Gas Spring Table, Hour Stool and Kettle Bell, incorporate pulleys, weights and levers ...