Movable pulley

Movable pulley 
In a moveable pulley, one end of the rope which passes around the pulley is tied to a firm support ‘O’ and effort ‘P’ is applied to the other end. The load is hung from the hook of the block. As the load is applied by two segments of rope,
the effort becomes twice of the applied value i.e.

EFFORT = 2 x P

In equilibrium condition we have

Load = Effort
W = 2P

Dividing both sides by P

W/P = 2

but [W/P = M.A]

thus

M.A. = 2

This shows that a moveable pulley can lift a load double the effort.