Q. A particle of mass M is situated at the centre of a spherical shell of same mass and radius a. The magnitude of the gravitational potential at a point situated at a/2 distance from the centre, will be
A) 4GM/a
B) GM/a
C) 2GM/a
D) 3GM/a
Explanation
[Solution from source] Potential due to the central particle at a/2 is −GM/(a/2) = −2GM/a; inside a shell the potential is constant at −GM/a. Total = −3GM/a, magnitude 3GM/a. Taking only the particle's contribution gives 2GM/a, forgetting that the shell's potential inside is not zero. Answer (4).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.