In theory the wheel and axle is nothing more than a single movable pulley, which instead of being a lever of the second class, and always lifting the weight exactly at its center, is a lever of the first class and lifts the weight some distance off the center. A single movable pulley moves the weight in the same direction in which the rope is pulled, but the wheel and axle moves the weight in the opposite direction from which the rope is pulled. The lengths of rope wound or unwound from the wheel and axle are always inversely proportional to the weights raised or lowered.