Mechanical advantage

The mechanical advantage of a mechanism (block and tackle, Z drag, lever, etc) is the factor by which a force is increased.

For example, the mechanical advantage of a Z drag is three. That means that a force of 1 unit applied to the end of the rope will pull the final pulley with a force of 3 units. The work done is the same - hence since force is work times distance, changing the force by three means that the smaller force has to be moved three times as far - that is, the end of the rope pulled with 1 unit of force will move three units of distance to move the pulley 1 unit of distance.