1. The problem statement, all variables and given/known data A sand-spraying locomotive sprays sand horizontally into a freight car situated ahead of it. The locomotive and freight car are not attached. The engineer in the locomotive maintains his speed so that the distance to the freight car is constant. The sand is transferred at a rate dm/dt = 10 kg/s with a velocity of 5 m/s relative to the locomotive. The car starts from rest with an initial mass of 2000 kg. Find its speed after 100 s. 2. Relevant equations 3. The attempt at a solution I am actually not sure how to start because of the given constraint that distance between the locomotive and car stays constant. Do I have to begin with evaluating P(t) and P(t+dt)? If so, what should be my system? Car and the incoming sand? Any help is appreciated. Thanks!