1. The problem statement, all variables and given/known data A railway wagon runs on frictionless rails and is pulled by an engine travelling at 10 ms−1 . The wagon is loaded at constant rate with 1000 kg of coal, dropped vertically from rest for a time of 2 s. What is the work done by the engine to keep the wagon moving at constant speed? Is the work done equal to the kinetic energy imparted to the coal and, if not, explain why not. 2. Relevant equations 3. The attempt at a solution Done the first part fine..Just unsure about the second part...I know the work-energy theorem..But am i right in thinking that the WD =/= KE imparted to coal as some KE of coal is lost as heat as it collides with the wagon on its descent?