question_answer 51)

                  A wheel in uniform motion about an axis passing through its centre and perpendicular to its plane is considered to be in mechanical (translational plus rotational) equilibrium because no net external force or torque is required to sustain its motion. However, the particles that constitute die wheel do experience a centripetal acceleration directed towards die centre. How do you reconcile this fact with the wheel being in equilibrium? How would you set a half-wheel into uniform motion about an axis passing through the centre of mass of the wheel and perpendicular to its plane? Will you require external forces to sustain the motion?                

Answer:

                  A particle experiences a centripetal acceleration, when moving with uniform speed in a circular path of radius r.                 In a half-wheel, mass is not distributed uniformly about its centre of mass. Therefore, external torque is needed to maintain its motion.