Two circular discs are of same thickness. The diameter of `A` is twice that of `B`. The moment of inertia of `A` as compared to that of `B` is

Options

A. twice
B. 4 times
C. 8 times
D. 16 times

Answer

D

Explanation

MI of a disc `=(1)/(2)MR^(2)`
`=(1)/(2)(piR^(2)t)rhoR^(2)=(1)/(2)pi R^(4)t rho`
It material and thickness(t) are same, then
`I prop R^(4)`
`(I_(A))/(I_(B))=(("Dimater or A")/("Dimeter of B"))^(4)=((2)/(1))=(16)/(1)`