A pulley makes work easier by redirecting and amplifying force. It helps reverse the direction of an individual’s lifting force. As a user pulls a rope down, the pulley lifts the weight up. When two ropes and wheels are used, a pulley reduces the effort needed to lift a weight by half.
For example, if an individual wants to lift an object that weighs 200 kilograms, the person only has to pull down with a force equivalent to 100 kilograms. A pulley with two ropes and wheels provides a mechanical advantage of two.
The measurement of the amount that a pulley multiplies force by is called mechanical advantage. With a larger mechanical advantage, a person requires less force, but the distance to use force increases. When raising an object 1 meter high, a person has to pull the rope by 2 meters. By using more wheels and a longer rope looping over them, the force needed to raise the weight into the air becomes much less.
A pulley that uses two ropes to support an object is called a movable pulley, and a pulley that uses only one rope is called a fixed pulley. Lifting the object requires the same amount of force to pull it down. However, it changes the direction of the force. This way, users leverage their own weight to add to the push, making work much easier.