Question

A composite disc to be made using equal masses of aluminimum and iron so that it has as high a moment of inertia as possible. This possible when.
A. The surfaces of the discs are made of iron with aluminimum inside
B. the whole of aluminimum is kept in the core and the iron at the outer rim of the disc
C. the whole of the iron is kepy in the core and the aluminimum at the outer rim of the disc
D. the whole disc is made with thin alternate sheets to iron and aluminimum.

Answer 1

Correct Answer - B
(b) We know density of iron gt density of aluminimum
Moment of inertia `I = I = int r^2 dm`.
:. Since, `rho_(iron) gt rho_(aluminimum)`
Hence to get high a moment of inertia whole of aluminimum is kept in the core and the iron at the outer rim of the disc.
.