A high-strength steel drill rod used for boring a hole in the earth has a diameter of 0.5 in. The allowable shear stress in the steel is 40 ksi and the shear modulus of elasticity is 11,600 ski.
(a) What is the minimum required length of the rod so that one end of the rod can be twisted 30 degrees with respect to the other end without exceeding the allowable stress?
(b) If the shear streain in part (a) is limited to 3.2 x 10^(-3), what is the minimum required length of the drill rodd?