2. Compare the torsional rigidities of the following sections a) a hollow tube 30 mm outside diameter and 1.5 mm thick
b) the same tube split along its length with a 1 mm gap
c) an equal leg angle section having the same perimeter and thickness as (b)
d) a square box section with side length 30 mm and 1.5 mm wall thickness
e) a rectangular solid bar, side ratio 2.5 to 1. having the same metal cross-sectional area
as the hollow tube. Compare also the maximum stress es arising in each case.​