Combination of Pulleys

Man's Way of Helping Himself:
A combination of pulleys called block and tackle is used where very heavy loads are to be moved. In Figure the upper block of pulleys is fixed, the lower block is movable, and one continuous rope passes around the various pulleys. The load is supported by 6 strands, and each strand bears one sixth of the load. If the hand pulls with a force of 1 pound at P, it can raise a load of 6 pounds at W, but the hand will have to pull downward 6 feet at P in order to raise the load at W 1 foot. If 8 pulleys were used, a force equivalent to one eighth of the load would suffice to move W, but this force would have to be exerted over a distance 8 times as great as that through which W was raised.

FIG. - An effective arrangement of pulleys known as block and tackle.