MyLeoNes™

Pulleys can make lifting easier — Physical education, 7–10 years

A pulley is a wheel with a groove for a rope. It can change the direction of a pull, and several pulleys can share the load.

A wheel guiding a rope

A pulley has a grooved wheel and a rope running around it. Pulling one end makes the other end move, so a load can rise. One fixed pulley may not reduce the total force, but it lets you pull down instead of awkwardly pulling up.

The lifting problem

Lifting a heavy object straight up can be hard and can put your body in an awkward position. People needed ways to raise water, sails and building materials more safely. A pulley changes the path of the rope; a pulley system can also spread the load across more rope sections.

Lifting a bucket

A bucket weighs 20 newtons. With one fixed pulley, you still need about 20 newtons of pull, but you can pull the rope downward. In a simple system with two rope sections supporting the bucket, each section carries about 10 newtons, so the needed pull is about 10 newtons, ignoring friction.

A pulley is not magic

It is easy to think every pulley makes a load lighter. A fixed pulley mainly changes the direction of the pull; it does not create energy or remove the load’s weight. Systems that need less force usually make you pull a longer length of rope, which is a fair trade.

Pulleys in the world

Flagpoles use a pulley so a person on the ground can raise a flag. Cranes use pulley systems to lift heavy loads on building sites, and some lifts use related arrangements. Each design is chosen for its job, because changing direction and reducing force are not exactly the same benefit.

Keep exploring

Other languages

Loading MyLeoNes™…