Pulley system, the massless and frictionless pulleys do not dissipate energy and allow for a change of direction of a rope that does not stretch or wear. In this case, a force balance on a free body that includes the load, "W", and "n" supporting sections of a rope with tension "T", yields: The ratio of the load to the input tension force is the mechanical advantage "MA" of the pulley system, Thus, the mechanical advantage of the system is equal to the number of sections of rope supporting the load. A belt and pulley system is characterised by two or
Block (sailing) matter is slightly complicated by the fact that every tackle has a "working end" where the final run of rope leaves the last sheave. More mechanical advantage can be obtained if this end is attached to the moving load rather than the fixed end of the tackle. There are various types of blocks that are used in sailing. Some blocks are used to increase mechanical advantage and others are used simply to change the direction of a line. A "ratchet block" turns freely when a line is pulled in one direction but does not turn the other direction, although the