An arrangement of two pulleys, as shown in the figure, is used to lift a 49.6-kg mass a distance of 3.70 m above the starting point. Assume the pulleys and rope are ideal and that all rope sections are essentially vertical.

Question

(a) What is the mechanical advantage of this system? (In other words, by what factor is the force you exert to lift the weight multiplied by the pulley system?)

(b) What is the change in the potential energy of the weight when it is lifted a distance of 3.70 m?
kJ
(c) How much work must be done to lift the 49.6-kg mass a distance of 3.70 m?
kJ

(d) What length of rope must be pulled by the person lifting the weight 3.70 m higher in the air?
m

Answer 1

a) The mechanical advantage of this system is 2.

b) The change in the potential energy of the weight when it is lifted a distance of 3.70 m is 472.32 kJ.

c) The work done to lift the 49.6-kg mass a distance of 3.70 m is 472.32 kJ.

d) The length of rope that must be pulled by the person lifting the weight 3.70 m higher in the air is 7.40 m.