Question

A circular disc is to be made by using iron and aluminium, so that it acquires maximum momentum of inertia about its geometrical axis. It is possible with

• A. Iron and aluminium layers in alternate order
• B. Aluminium at interior and iron surrounding it
• C. Iron at interior and aluminium surrounding it
• D. Either (a) or (c)

Answer 1

Answer: (B)

Aluminium at interior and iron surrounding it

A disc is composed of rings and moment of inertia of disk can be found by using integral of moment of inertia of concentric elemental rings.

Moment of inertia of continuous body is found by using $I=\int R^{2}dm$.

For increasing the moment of inertia of a non-uniform disc, it is hence desired that the mass density is more in the exterior parts of the disc.

Thus, B is the correct option.