Pulleys

A pulley is a kind of wheel with two raised edges that a rope runs along. You can use pulleys in different way, to make it easier to pull a rope, to change the direction of the force, or to get more mechanical advantage and lift something heavier than you could usually lift by yourself.

 

This clothesline uses a fixed pulley.

A fixed pulley is attached to a hook or a wall and doesn't move. It doesn't change the force needed to lift something but can change the direction of the force, that is you can pull down to lift something up.
A moveable pulley gives you a mechanical advantage. This means you can pull with less force for longer distance to get the same work done. This means you can lift things that would usually be too heavy to lift without a pulley.

By Emily