A man of mass `m_1` is standing on a platform of mass `m_2` kept on a smooth horizontal surface. The man starts moving on the platform with a velocity `v_r` relative to the platform. Find the recoil velocity of platform.

Explanation

Absolute velocity of man = `v_(r) – v` where v = recoil velocity of platform. Taking the platform and the man a system, net external force on the system in horizontal direction is zero. The linear momentum of the system remains constant. Initially both the man and the platform were at rest.

Hence, `0=m_(1)(v_(r)-v)-m_(2)v`
`thereforev=(m_(1)v_(r))/(m_(1)+m_(2))`