The electric motor exerts a torque of 800 N-m on the steel shaft ABCD when it is rotating at a constant speed. Design specifications require that the diameter of the

shaft be uniform from A to D and that the angle of twist between A and D not exceed 1.5°. Knowing that t max S 60 MPa and G=77.2 GPa,determine the minimum diameter shaft that can be used.

Fig: 1

Fig: 2