Question

Find the moment of inertia of a hoop (a thin-walled, hollow ring) with mass MMM and radius RRR about an axis perpendicular to the hoop's plane at an edge.

Answer 1

I = sum m *r^2 where m represents the (small) individual masses and r is the distance of that mass from center of rotation

Note: sum m = M

For the hoop given all masses are at a distance RRR from the center of rotation

I = MMM * RRR^2