1.

Two discs have same mass and thickness. Their materials are of densities rho_(1)andrho_(2). The ratio of their moment of inertia about central axis will be :

Answer»

`rho_(1):rho_(2)`
`rho_(1)rho_(1):1`
`1:rho_(1)rho_(2)`
`rho_(2):rho_(1)`

Solution :Here `I_(1)=(1)/(2)mr_(1)^(2)andI_(2)=(1)/(2)mr_(2)^(2)`
`therefore (I_(1))/(I_(2))=(r_(1)^(2))/(r_(2)^(2))` ALSO if `.rho.` is the thickness
`pir_(1)^(2)rho_(1)=pir_(2)^(2)rho_(2)` (masses EQUAL)
`therefore (r_(1)^(2))/(r_(2)^(2))=(rho_(2))/(rho_(1))=(I_(1))/(I_(1))=(rho_(2))/(rho_(1))`


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