As the tension in the cable on each side of the lower pulley (2) is equal to the force ( P), the mechanical advantage is (2:1), meaning the force ( P) is half the magnitude of the load (W ). Also, as the force ( P) moves downward the lower pulley (2) rolls like a wheel up the cable that is attached to the center of the upper pulley (1). From the last section on rolling wheels, the velocity of the center of a wheel is half the velocity at a point at the top of the wheel. Therefore, the velocity (vW ) of the load (W ), which is equal to the velocity of the center of the lower pulley (2), is half the velocity (vP ) of the force ( P) and given by Eq. (10.58) as