5-2. The solid shaft of radius is subjected to a torque T. Determine the radius r' of the inner core of the shaft that resists one-half of the applied torque (T/2). Solve the problem two ways: (a) by using the torsion formula, (b) by finding the resultant of the shear-stress distribution. *5-36. The drive shaft of a tractor is made of a steel tube having an allowable shear stress of Tallow = 6 ksi. If the outer diameter is 3 in. and the engine delivers 175 hp to the shaft when it is turning at 1250 rev/min, determine the minimum required thickness of the shaft's wall. 5-12. The solid shaft is fixed to the support at C and subjected to the torsional loadings shown. Determine the shear stress at points A and B and sketch the shear stress on volume elements located at these points. 35 mm- 35 mm 20 mm 300 N-m 800 N-m