## Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (4th Edition)

$v = \sqrt{\frac{m_2~g~r}{m_1}}$
The weight of $m_2$ should be equal to the centripetal force required to keep $m_1$ moving in a circle. We can find the required speed of $m_1$ as; $F_c = \frac{m_1~v^2}{r} = m_2~g$ $v^2 = \frac{m_2~g~r}{m_1}$ $v = \sqrt{\frac{m_2~g~r}{m_1}}$