A solid sphere of radius `a` and mass `m` is surrounded by cocentric spherical shell of thickness `2a` and mass `2m` the gravitational field at a distance 3a from their centres is

Options

A. `(GM)/(9a^(2))`
B. `(2GM)/(9a^(2))`
C. `(GM)/(3d^(2))`
D. `(2GM)/(3a^(2))`

Answer

C

Explanation

`E_(p)=(GM)/((3a)^(2))+(G.2M)/((3a)^(2))=(GM)/(3a^(2))`