Question

A circular disc ${}^{\prime }{A}^{\prime }$ of radius ${}^{\prime }{r}^{\prime }$ is made from an iron plate of thickness $t$ and another circular disc ${}^{\prime }{B}^{\prime }$ of radius $4r$ is made from an iron plate of thickness $t/4$. The relation between the moments of inertia $I_A$ and $I_B$ is:

• A. $I_A>I_B$
• B. $I_A=I_B$
• C. $I_A<I_B$
• D. The conditions are insufficient to predict the relation between $I_A$ and $I_B$

Answer 1

Answer: (A), (C)

The correct options are
A $I_A>I_B$
C $I_A<I_B$

Moment Of Inertia = I =
Mass =Density* Volume
Let d be the density of both the iron plates.
Using the above equations,
=
=
Therefore,