1. The problem statement, all variables and given/known data I am trying to work the moment of inertia for a) rotating rod, axis through the centre of the rod http://hyperphysics.phy-astr.gsu.edu/hbase/mi2.html#irod3 b) Solid cylinder http://hyperphysics.phy-astr.gsu.edu/hbase/icyl.html#icyl2 2. Relevant equations I = R^2 dM 3. The attempt at a solution I understand all of the steps, except the limits of integration in terms of R or L. For the rod, the limit of integration is from L/2 to -L/2 Why is the limit of integration for the cylinder from R to 0? Should it be from the end to end? R to -R?