Block and tackle in the line that either attach to or run through the moving blocks—in other words, the number of supporting rope sections. An ideal block and tackle with a moving block supported by "n" rope sections has the mechanical advantage (MA), where F is the hauling (or input) force and F is the load. Consider the set of pulleys that form the moving block and the parts of the rope that support this block. If there are "n" of these parts of the rope supporting the load "F," then a force balance on the moving block shows that the tension in
Block and tackle each of the parts of the rope must be "F/n." This means the input force on the rope is "F"="F/n." Thus, the block and tackle reduces the input force by the factor "n." Ideal mechanical advantage correlates directly with velocity ratio. The velocity ratio of a tackle is the ratio between the velocity of the hauling line to that of the hauled load. A line with a mechanical advantage of 4 has a velocity ratio of 4:1. In other words, to raise a load at 1 metre per second, the hauling part of the rope must be pulled at 4