1. The problem statement, all variables and given/known data A(50 kg) and B(60 kg) are sitting at the two extremes of a 4m long boat,standing still in water.They came at the middle.Neglecting water friction,find the displacement of the boat 2. Relevant equations 3. The attempt at a solution I did it in the following way.Check if I am right. I first found the initial position of CM=(32/15)m [A at 0,B at 4m,Boat CM at 2m] I then found the final position of CM=2m So,displacement of the CM=[(32/15)-2](-i) m assuming x axis pointing right. This gives displacement~13.3 m which is close to given answer 13cm. But I am not convinced.Since,there is no external force,the CM should be static... Please help.