Two bodies of masses $m_1$ and $m_2$ are initially at rest placed infinite distance apart. They are then allowed to move towards each other under their mutual gravitational attraction. Their relative velocity when they are 'r' distance apart is

Question

$$(a)\;\sqrt {\frac{2G(m_1+m_2)}{r}} \quad (b)\; \sqrt {\frac{2Gm_1m_2}{(m_1+m_2)r}}\quad (c)\;\sqrt {\frac{G(m_1+m_2)}{r}} \quad (d)\;\sqrt {\frac{G(m_1m_2)}{(m_1+m_+2)r}}$$

Comments

Mam how mew is equal to m1m2/m1+m2