Suppose you use an ideal pulley of the type shown in Figure

Suppose you use an ideal pulley of the type shown in Figure 5.18(b) and find it necessary to exert a force of 110 N to support a load.

(a) What is the load\'s mass?
_______________ kg

(b) What force is exerted on the ceiling? Neglect the pulley system\'s mass.
_______________ N (upward)

Solution

According to the problem,

Assuming g = 9.81 m/s² and ignore the slight angles the rope makes with vertical

a) Use a free body diagram of the lower pulley, sum vertical forces to zero

2T - mg = 0
T = 539 N

b) Use a free body diagram of the upper pulley, sum vertical forces to zero

F - 3T = 0
F = 1617 N upward.