Question

Fig 3.39 shows a system of four pulleys, The upper two pulleys are fixed and the lower two are movable.

(a) Draw a string around the pulleys. Also show the place and direction in which the effort if applied.

(b) What is the velocity ratio of the system?

(c) How are load and effort of the pulley system related?

(d) What assumption do you make in arriving at your answer in part(c)?

Answer 1

(b) Velocity ratio of the system = n = 4

(c) The relation between load and effort

MA = Load/effort = n = 4

(d)

(i) There is no friction in the pulley bearing,

(ii) weight of lower pulleys is negligible and

(iii) the effort is applied downwards.