1. The problem statement, all variables and given/known data 2. Relevant equations -given in question 3. The attempt at a solution I am bit confused with the boundary conditions of this problem. I understand the radial stress is zero on the inside diameter and the radial stress on the outside diameter will be the reaction to the centripetal force per m^2. So surely you need a width to calculate the radial stress on the outside diameter which isn't given in the question?