Two discs of same material have the same mass. If their thickness are in the ratio `1:3`, then their moment of inertia are in the ratio

Options

A. `1:sqrt(3)`
B. `1:3`
C. `3:1`
D. `1:9`

Answer

C

Explanation

Since the discs have same mass
`:.(r_(1)^(2))/(r_(2)^(2))=(t_(2))/(t_(1))=3/1`
`(I_(1))/(I_(2))=(1//2mr_(1)^(2))/(1//2mr_(2)^(2))=(r_(1)^(2))/(r_(2)^(2))`
`:.(I_(1))/(I_(2))=(t_(2))/(t_(1))=3/1`
`:.I_(1):I_(2)=3:1`