A uniform disc of radius `R` lies in the `x-y` plane, with its centre at origin. Its moment of inertia about z-axis is equal to its moment of inertia about line `y = x + c`. The value of `c` will be.
.

Options

A. `-R/2`
B. `+-R/(sqrt(2))`
C. `+R/4`
D. `-R`

Answer

B

Explanation

`I_(PQR)=I_(AOB)+M(ON)^(2)`
`=1/2MR^(2)+M(c/sqrt2)^(2)`
`But =1/4MR^(2)=l_(2)`
`c=+-R/(sqrt(2))`