1. The problem statement, all variables and given/known data 2. Relevant equations 3. The attempt at a solution When the particle of mass M/2 collides with the pan ,an impulsive tension acts on the (pan+particle) . Let us call this J . Tension acting in the string between the two blocks is T . Speed of particle before collision = u = √(gl) Speed of (pan+particle) after collision = v Applying impulse momentum theorem on (pan+particle), Mu/2 -J = Mv/2 Applying impulse momentum theorem on block A, J = Mv From the above two equations we get v = √(gl)/3 . Is my reasoning correct ? How should I proceed ? I would be grateful if somebody could help me with the problem .