Calculate the circumferential (hoop) stress on a thin-walled pressure tank that experiences an internal pressure of 4 MPa and an external pressure of 2.5 MPa. The tank wall thickness is 50 mm and its inner diameter is 200 mm.

A 40 cm long and 10 cm diameter brass cylinder was subjected to a tensile load of 50,000 N. The resulting increase in length and decrease in diameter were noted to be 0.8 mm and 0.05 mm respectively. Find the Poisson's ratio of brass.

A shaft of 60 mm diameter subjected to torsion has a shear strain of 0.0006 at the outer surface. The rate of twist will be equal to: