5.19 What is the torsional spring constant (torque per degree of angular deflection) in N ⋅ m / deg . for a solid round steel shaft 400 mm long if its diameter is 30 mm? 20 mm? 30 mm for half its length and 20 mm for the other half?

Avertical steel rod of length 2.0 m and diameter 25 mm is rigidly fixed at its upper end and has a flange at its lower, free, end. what will be the maximum stress produced in the rod when a load of 20 kn is applied, (a) gradually to the lower end, (b) suddenly to the lower end, (c) by a collar falling from a height of 50 mm on to the flange?