A collar `B` of mass `m` is at rest and when it is in the position shown, the spring is unstretched. If another collar `A` of mass `(m)/(n)` strikes it so that `B` slides a distance `4m` on the smooth rod before momentarily stopping, determine the velocity of `A` just after the impact. The coefficient of restitution is `e`. The spring constant is `k`.
`2(1-etae)/(1+e)sqrt((k)/(m))`