A single fixed pulley makes it easier to lift a weight by allowing you to pull down on a rope rather than lift the weight up.
If you want to move the same weight with less effort, you need to use a multiple pulley system.
In the two pulley system shown opposite, the effort is half that
required in the single pulley system. This pulley system is a force
multiplier.
However, the rope must be pulled through twice the distance.
To examine the effect of adding more pulleys, visit the on-line experiment.
Click on the image to animate it. Notice
that the hand holding the rope moves more or less twice the distance that
the load does.