Q: Two particles of equal mass go round a circle of radius R under the action of their mutual gravitational attraction. The speed of each particle is

(a) $v = \frac{1}{2 R}\sqrt{\frac{1}{G m}}$

(b) $v = \sqrt{\frac{G m}{6 R}}$

(c) $v = \frac{1}{2 }\sqrt{\frac{G m}{R}}$

(d) $ v = \sqrt{\frac{4 G m}{R}}$

Ans: (c)