A solid sphere of mass `M`, radius `R` and having moment of inertia about as axis passing through the centre of mass as `I`, is recast into a disc of thickness `t`, whose moment of inertia about an axis passing through its edge and perpendicular to its plance remains `I`. Then, radius of the disc will be.

Options

A. `(2R)/(sqrt15)`
B. `Rsqrt((2)/(15))`
C. `(4R)/(sqrt15)`
D. `(R )/(4)`

Explanation

`(2)/(5)MR^(2)=((1)/(2)Mr^(2)+Mr^(2))=(3)/(2)Mr^(2)`
`r=(2R)/(sqrt15)`