Two disc have same mass and thickness. Their materials have densities `d_(1) and d_(2)` . The ratio of their moment of inertia about central axis will be

Options

A. `d_(1):d_(2)`
B. `d_(1)d_(2):1`
C. `1:d_(1)d_(2)`
D. `d_(2):d_(1)`

Answer

D

Explanation

As `m_(1)=m_(2) rArr piR_(1)^(2)xxd_(1)=piR_(2)^(2)xxd_(2) or (R_(1)^(2))/(R_(2)^(2))=(d_(2))/(d_(1))`
`"Now, "(l_(1))/(l_(2))=((1)/(2)mR_(1)^(2))/((1)/(2)mR_(2)^(2))=(R_(1)^(2))/(R_(2)^(2))=(d_(2))/(d_(1))`