(3) With the additional pulley, the force required has decreased. Where does the corresponding increase occur?
Although half the force is now required, twice the cord length is needed to lift the mass to the same height. When lifting the mass by hand, the distance covered is some h. When using the first pulley system, both cords must cover the distance h, so the total cord used is 2h. After adding the pulley, the length of rope needed is 4h.
(4) If the amount of force required is less (an advantage), what is the corresponding disadvantage?
Although the mass may feel easier to lift with the help of pulleys, the system as a whole is less efficient:
Efficiency loss is caused by the physical nature of the systems: more surfaces subject to friction and the weight of the pulleys, for example.
