Clouds/Trees 1

Pulley

by Daniel

A pulley is made from a wheel and a rope. It is used to make lifting easier. A single pulley changes the direction of the lifting force. For example, if you are lifting a heavy object with a single pulley anchored to the ceiling, you can pull down on the rope to lift the object instead of pushing up. The same amount of effort is needed as without a pulley, but it feels easier because you are pulling down. If you add a second pulley, the amount of effort to lift the heavy object is much less -- half as much. However, you will have to pull the rope further. A double pulley can help you to lift objects you could never lift without it.

Pulleys are also used on elevators. Remember the elevator in the book? If you would like to build an elevator using K'nex, click here . Pulleys are also used on cranes to hoist things up. Can you think of other pulleys you have seen? Look at the pictures below to see some pulleys I found. To see animated pulleys, click here .

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Clouds/Trees 1