A pulley is a simple machine with two parts. A pulley has a cord or chain that is wrapped around a wheel. When you pull down on one cord or chain, the wheel turns and the other end of the cord or chain moves up. The pulley helps lift or pull things that are heavy. Cranes use pulleys to lift heavy objects like steel beams. The wheel in the middle of a pulley is called a fulcrum.
Fixed pulleys have fulcrums in the middle and do not move up and down themselves. An example of a fixed pulley is the pulley used to lift a sail on a sailboat. Moveable pulleys are free to move up and down (the fulcrum can move and one end of the cord or chain can move). A moveable pulley is attached to something heavy to lift it. Have you seen cartoons where people are trying to lift a heavy piano to get it into an apartment? They are using moveable pulleys to do this.
Have you ever raised a flag on a flagpole? There is a special pulley at the top of the flagpole that helps lift the flag into place.
Picture taken by Peyton
A tape dispenser has several simple machines, including a pulley and a screw.
Picture by Bailey
To learn more about pulleys, visit this site: http://www.factmonster.com/ce6/sci/A0840500.html
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