The figure shows two solid discs with radius $R$ and $r$ respectively. If mass per unit area is the same for both, what is the ratio of MI of bigger disc around axis $AB$ (which is $\perp$ to the plane of the disc and passing through its centre) to MI of smaller disc around one of its diameters lying on its plane? Given $M$ is the mass of the larger disc. (MI stands for moment of inertia) (1) $R ^ { 2 } : r ^ { 2 }$ (2) $2 r ^ { 4 } : R ^ { 4 }$ (3) $2 R ^ { 2 } : r ^ { 2 }$ (4) $2 R ^ { 4 } : r ^ { 4 }$
The figure shows two solid discs with radius $R$ and $r$ respectively. If mass per unit area is the same for both, what is the ratio of MI of bigger disc around axis $AB$ (which is $\perp$ to the plane of the disc and passing through its centre) to MI of smaller disc around one of its diameters lying on its plane? Given $M$ is the mass of the larger disc. (MI stands for moment of inertia)\\
(1) $R ^ { 2 } : r ^ { 2 }$\\
(2) $2 r ^ { 4 } : R ^ { 4 }$\\
(3) $2 R ^ { 2 } : r ^ { 2 }$\\
(4) $2 R ^ { 4 } : r ^ { 4 }$