Question

A circular disc is to be made using iron and aluminium. To keep its moment of inertia maximum about a geometrical axis, it should be so prepared that

• A. aluminium at interior and iron surrounds it
• B. iron at interior and aluminium surrounds a
• C. aluminium and iron layers in alternate order
• D. sheet of iron is used at both external surfaces and aluminium sheet as inner material

Answer 1

The correct option is A aluminium at interior and iron surrounds it

We know that$,$

Moment of inertia $=M{R}^2$

Now$,$

the atomic mass of iron is much greater than the atomic mass of aluminium and thus for moment of inertia to be maximum iron should placed further away from the geometrical axis and aluminium should be placed closer to it$.$

So$,$ aluminium should be in the interior with iron surrounding it$.$

Hence,

option $\left(A\right)$ is correct answer.