What will be the factor of safety if the

Question

The diameter of a solid shaft made of mild steel, rotating at 250 r.p.m. is 45mm. The shaft is designed to transmit 50 kW. What will be the factor of safety if the ultimate shear stress at yield is 427 N/mm²?

(a) 6            (b) 5           (c) 4          (d) 3