angular deflection between the ends

Question

A torque of 10 N-m is transmitted through a stepped shaft as shown in figure. The torsional stiffnesses of individual sections of lengths MN, NO and OP are 20 N-m/rad, 30 N-m/rad and 60 N-m/rad respectively. The angular deflection between the ends M and P of the shaft is

(a) 0.5 rad

(b) 1.0 rad

(c) 5.0 rad

(d) 10.0 rad

Answer 1

Given a stepped shaft in which torque is transmitted