This diagram of four
pulley systems illustrates how increasing the number of pulleys increases the
mechanical advantage, making the load easier to lift. MA is the factor by which a mechanism multiplies the
force put into it. In this diagram, 100
newtons is required to lift the weight off the ground. Each additional pulley increases the MA such that the four-pulley system only needs 25 newtons to accomplish the same task, but the rope must be pulled four times as far.
Image credit: Prolineserver/Tomia