A solid sphere of mass `m &` rdius `R` is divided in two parts of `m` mass `(7m)/(8) & (m)/(8)`, and converted to a disc of radius `2R &` solid sphere of radius `'r'` respectively. Find `(I_(1))/(I_(2))` , If `I_(1) & I_(2)` are moment of inertia of disc `&` solid sphere respectively

Options

A. 285
B. 185
C. 140
D. 65

Answer

C

Explanation

`I_(1) = (7M)/8 xx (2R)^(2)/2 = 7/4 MR^(2), I_(2) = 2/5 xx (M/6) xx (R/2)^(2)` (Radius of new sphere `=R/2`) `=1/80 MR^(2)`
`I_(1) + I_(2) = 140`