Two bodies 1 and 2 of masses m and M are kept slightly separated . A third body 3 of mass m coming from left with velocity v makes a head- on elastic collision with m . Show that if `m ge M ` there are exactly two collisions and find all final velocities and if `m le M` there are three collisions and find all final velocities .

Answer

`v_(3) = 0 , v_(1) = v(m-M)/(m + M) , v_(2) = (2vm)/(m + M) ; v_(3) = -(v(M-m))/(M + m) v_(1) = 0 , v_(2) = (2vm)/(m + M)`