What Are Some Facts About Pulleys?

Elevators use pulleys as they move the passenger compartments up and down from one floor to the next. Drapery and window blinds also use pulleys -- much smaller than the ones for elevators -- to move the blinds or drapes around.

A pulley is really a combination of a chain, rope or cord with an axle and wheel. It is possible to combine multiple pulleys within a system to cut down on the work that is needed to lift significant loads or bring them down to a lower level.

Pulleys also make moving an object upward simpler to do while remaining on the ground, because the pulley alters the direction in which work must take place. Hoisting a flag on a flagpole is simple with a pulley, because all the person has to do is pull down on a rope; the rope snakes around the pulley, does a 180-degree turn, and starts pulling upward. A similar process works when someone hoists a sail on a boat. Pulling down on a rope makes a sail rise up into the air so it can catch the wind.

Fixed pulleys remain in one place while the rope or cord moves, while moving pulleys glide along with the rope while still reducing the work load. A block and tackle combines a moving pulley on the load with a fixed pulley on the support structure above.