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7.Gravitation
normal
Two particles of equal mass $'m'$ go around a circle of radius $R$ under the action of their mutual gravitational attraction. The speed of each particle with respect to their centre of mass is
A
$\sqrt {\frac{{Gm}}{R}} $
B
$\sqrt {\frac{{Gm}}{{4R}}} $
C
$\sqrt {\frac{{Gm}}{{3R}}} $
D
$\sqrt {\frac{{Gm}}{{2R}}} $
Solution

As gravitational force provides necessary centripetal force.
i.e., $\quad F=\frac{G m^{2}}{(2 R)^{2}}=\frac{m v^{2}}{R} \Rightarrow v=\sqrt{\frac{G m}{4 R}}$
Standard 11
Physics