The required length of the key would be

Question

A shaft of 50 mm diameter transmits a torque of 800 N-m. The width of rectangular key used is 10 mm. the allowable shear stress of the material of the key being 40 MPa, the required length of the key would be                        

         (a) 60 mm                   (b) 70 mm

         (c) 80 mm                   (d) 90 mm