Describe the uses of compound pulleys

It is used to pull ships onto land and to get water from a well. Archimedes invented the compound pulley in ancient Greece.

All pulleys are used to change the direction of a force. That's what pulleys do.

A compound pulley also does something more. It's used to provide mechanical

advantage, so that the force pulling on the rope is multiplied to a greater force

that eventually pulls on the load.

Distance is given up ... the compound pulley may take the force you apply to

the rope, and make it five times stronger when it's applied to the load, but in

return for that extra force, you have to pull the rope five times farther than the

distance that the load moves.

For example: If you need to left a 600-pound crate, you can do it with a

compound pulley that has a mechanical advantage of 6. With that set up,

you can pull on the rope with a force of 100 pounds, and the 600-pound crate

will lift off the floor. BUT ... you have to pull 6-feet of rope in order to lift the

crate 1-foot off the floor.