Question

The value of the gravitational potential at the centre of a ring of radius “a” and mass “M” is _____

(a) zero

(b) -(G*M)/a

(c) -(G*M)/a^1/2

(d) infinite

This question was addressed to me in an interview.

This intriguing question comes from Gravitational Potential Energy in division Gravitation of Physics – Class 11

Answer 1

Right choice is (b) -(G*M)/a

Explanation: We know that the gravitational potential at a point “p” at a distance of “r” from the centre of the ring of radius “a” and mass M” is;

V = -(G*M)/(a^2+r^2)^1/2

At the centre of the ring; r = 0.

Therefore; V = -(G*M)/a.