A wheel is a stiff elastic body with a consistent motion that passes through its center, perpendicular to the wheel’s plane. Due to elastic force, every particle of the wheel receives a centripetal acceleration. Due to this, it is directed towards the axis of rotation. When the wheel is half-turned, the mass distribution is similarly half-turned. There is no symmetry in the wheel when the mass is halved. As a result, the angular momentum and the angular velocity do not match. Hence, external torque is needed.
A wheel in uniform motion about an axis passing through its centre and perpendicular to its plane is considered to be in mechanical equilibrium because no net external force or torque is required to sustain its motion. However, the particles that constitute the wheel do experience a centripetal acceleration directed towards the 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?
A wheel in uniform motion about an axis passing through its centre and perpendicular to its plane is considered to be in mechanical equilibrium because no net external force or torque is required to sustain its motion. However, the particles that constitute the wheel do experience a centripetal acceleration directed towards the 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?