A flexible shaft consists of a 0.20-in.-diameter steel rod encased in a stationary tube that fits closely enough to impose a torque of intensity 0.50 lb in./in. on the rod.
(a) Determine the maximum length of the shaft if the shear stress in the rod is not to exceed 20 ksi.
(b) What will be the relative angular rotation between the ends of the rod? Use G = 12 × 106 psi for steel.