A wheel in uniform motion about an axis passing through its centre and perpendicular plus is considered to be in mechanical (translational plus rotational ) equilibrium because no net external force or torqure is reqired to sustain its motion However , the particles than constitute the wheel do experience a centripeteal the acceleration wheel being in equilibrium ?
how would you set a half wheel into unifrom motion about an axis passing throgh the centre of mass of the wheel and perpendicular to its plane ? will ypu require external forces to sustain the motion ?

Explanation

A wheel is a rigid body. The centripetal accelerations of the particle of the wheel arise due to the internal elastic forces which cancel out in paries.
In a half wheel, the distribution of mass about its centre of mass (through which axis of rotation passes) is not symmertical. Therefore, the direction of angular momentum of the wheel does not coincide with the direction of its angular velocity. Hence, an external torque is required to maintain the motion of the half wheel.