A particle of mass M is at the centre of a spherical shell having the same mass M and radius a. What is the magnitude of the gravitational potential at a point a/2 from the centre?
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A particle of mass M is at the centre of a spherical shell having the same mass M and radius a. What is the magnitude of the gravitational potential at a point a/2 from the centre?

G1 Physics · Accepted Answer

Step 1: Inside a thin spherical shell, its potential is constant V(shell)=−GM/a. Step 2: The central point mass contributes V(point)=−GM/(a/2)=−2GM/a. Sum is −3GM/a; its magnitude is 3GM/a. Final answer: B — 3GM/a.