Two thin rings of masses m1 and m2, each of radius R are coaxially placed at a distance R. If the rings have a uniform mass distribution then the work done in moving a mass m from centre of one ring to that of the other is:

Q: Two thin rings of masses m1 and m2, each of radius R are coaxially placed at a distance R. If the rings have a uniform mass distribution then the work done in moving a mass m from centre of one ring to that of the other is:

(a) $\frac{G m(m_1 + m_2)(\sqrt{2}-1)}{\sqrt{2} R}$

(b) $\frac{G m(m_1 – m_2)(\sqrt{2}-1)}{\sqrt{2} R}$

(c) $\frac{G m \sqrt{2}(m_1 + m_2)}{R}$

(d) Zero

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Ans: (b)