A 15-cm-diameter CD has a mass of 25 g. A. What is the CD's moment of inertia for rotation about a perpendicular axis through its center?B. What is the CD's moment of inertia for rotation about a perpendicular axis through the edge of the disk?

Solution :

The moment of inertia for a circular disc about its centre is given by

Given , radius of CD,

A).

The moment of inertia of CD about its centre is

B).

The moment of inertia about parallel axis of CD with respect to its central axis is given by the parallel axis theorem,

where, d is the distance between the parallel axis and central axis

Therefore, moment of inertia of CD about its edge is

convex lenses are thicker at the middle. rays of light that pass through the lens are brought closer together (they converge). a convex lens is a converging lens. when parallel rays of light pass through a convex lens the refracted rays converge at one point called the principal focus.