Question

Two circular disc of same mass and thickness are made from metals having densities `rho_(1)` and `rho_(2)` respectively. The ratio of their moment of inertia about an axis passing through its centre is,
A. `rho_(1): rho_(2)`
B. `rho_(1)rho_(2):1`
C. `rho_(2):rho_(1)`
D. `1 : rho_(1)rho_(2)`

Answer 1

Correct Answer - C
`(I_(1))/(I_(2))=(R_(1)^(2))/(R_(2)^(2))`
and `rho_(1)=(m_(1))/(A_(1)) " " rho_(2)=(m_(2))/(A_(2))`
`therefore (rho_(1))/(rho_(2))=(A_(2))/(A_(1))=(R_(2)^(2))/(R_(1)^(2))`