Question 695: Centre of Mass and Rotational Motion

Question

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

Accepted Answer

A circular disc may be divided into a large number of circular rings. Moment of inertia of the disc will be the summation of the moments of inertia of these rings about the geometrical axis.
Now, moment of inertia of a circular ring about its geometrical axis is MR
2
, where M is the mass and R is the radius of the ring.
Since the density (mass per unit volume) for iron is more than that of aluminium, the proposed rings made of iron should be placed at a higher radius to get more value of MR
2
. Hence to get maximum moment of inertia for the circular disc, aluminium should be placed at interior and iron at the outside.

Answer

aluminium at interior and iron surround to it

Answer

iron at interior and aluminium surround to it

Answer

using iron and aluminium layers in alternate order

Answer

sheet of iron is used at both external surface and aluminium sheet as internal layers.

Centre of Mass and Rotational Motion

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

Choose the correct answer: