Two rings of radius R and n R made up of same material have the ratio of moment of inertia about an axis passing through centre is \[4\]. The value of n is
A) \[\frac{1}{2}\]
B) \[60m\]
C) \[50m\]
D) \[30m\]
Correct Answer:
A
Solution :
Ratio of moment of inertia of the rings \[2.80\times {{10}^{5}}\] \[{{10}^{4}}\Omega \] (\[10\Omega \] = linear density of wire = constant) \[4.62\times {{10}^{-2}}\] \[2.03\times {{10}^{-2}}\] (given) \[3.16\times {{10}^{-2}}\] \[5.62\text{ }\times {{10}^{-2}}\] \[\lambda \] \[\lambda \,\,\,\,\pi {{r}^{3}}\frac{dB}{dt}\]