1. The problem statement, all variables and given/known data A trolley of mass 2.4Kg is moving along a smooth horizontal surface with a constant speed of 2.0m/s when a brick of mass 1.5Kg is dropped vertically on to it. What is the change in momentum of the trolley? 2. Relevant equations Impulse: F(delt)=m(delv) momentum: mv 3. The attempt at a solution I don't understand the question very well. As far as I can see there isn't enough data. I don't know how fast the trolley is moving after the brick has landed. Conservation of momentum can't be used because I don't know the initial momentum.