Q: Three objects, each of mass m are at the vertices of an equilateral triangle and these vertices are on the circumference of a circle of radius R. These three objects are rotating on the circle under their mutual gravitational force of attraction. What is the speed of each mass?

(a) $(\frac{G m}{\sqrt{5 R}})^{1/2}$

(b) $(\frac{G m}{\sqrt{6 R}})^{1/2}$

(c) $(\frac{G m}{\sqrt{2 R}})^{1/2}$

(d) $(\frac{G m}{\sqrt{3 R}})^{1/2}$

Ans: (d)