1. Calculate the shear stresses at the outer and inner surfaces of a hollow circular steel shaft subjected to a torque of 350,000 lb-in. The outside diameter of the shaft is 6 in. and the inside diameter is 3 in.
2. A hollow shaft is produced by boring a 150-mm-diameter concentric core in a 225-mm-diameter solid circular shaft. Compute the percentage of the torsional strength lost.