A particle of mass M is placed at the centre of a uniform spherical shell of equal m as and radius a. Find the gravitational potential at a point P at a distance a/2 from the centre.

Explanation

The gravitational potential at the point P due to the particle at the centre is `V_1=-(GM)/(a//2)=-(2GM)/a`
The potential at P due to the shell is `V_2=-(Gm)/a`
The net potential at P is `V_1+V_2=-(3Gm)/a`