The rule works for a circular or elliptical cylinder rotated about the cylinder axis, or for a circular or elliptical disk about any of the axes of symmetry. What is the moment of inertia of a circula...The rule works for a circular or elliptical cylinder rotated about the cylinder axis, or for a circular or elliptical disk about any of the axes of symmetry. What is the moment of inertia of a circular disk of radius R rotated about an axis perpendicular to the plane of the disk and passing through its center.