 Like the velocities "F"A is directed downwards and "F"B is directed upwards.For an ideal block and tackle system there is no friction in the pulleys and no deflection or wear in the rope, which means the power input by the applied force "F"A"V"A must equal the power out acting on the load "F"B"V"B, that is

The ratio of the output force to the input force is the mechanical advantage of an ideal gun tackle system,

This analysis generalizes to an ideal block and tackle with a moving block supported by "n" rope sections,

This shows that the force exerted by an ideal block and tackle is "n" times the input force, where "n" is the number of sections of rope that support the moving block.Mechanical advantage that is computed using the assumption that no power is lost through deflection, friction and wear of a machine is the maximum performance that can be achieved.