What is a pulley?
A pulley is a simple machine that helps lift and lower objects. It is a special kind of wheel & axle with a rope, chain, or wire around it. There is a groove around the outside of the wheel to keep the rope, chain, or wire in place. A pulley does work by changing the direction of the force, allowing objects to be raised.
Types of Pulleys
In a fixed pulley, the wheel turns, but the pulley itself does not move. This type of pulley changes the direction of effort. When you pull the rope downward, the load moves upward. The distance of the effort applied is the same as the distance the object moves.
In a movable pulley, the load is attached to the pulley. In this type of pulley, the direction of effort does not change. However, the load is supported by rope on both sides of the pulley. Therefore, you need half as much effort to lift the load.
How are pulleys used?
Pulleys are used to help us move things up and down.
Where are pulleys found?
Pulleys can be found both inside and outside. Flags are raised by a fixed pulley on a flag pole, and are found outside. Pulling down on the rope causes the flag to move up the flag pole. Elevators have movable pulleys to help them lift heavy loads, and can be found inside. The load is attached to the pulley, so half the effort is needed.