Two trains travel on parallel tracks that are 5 km long. One starts at the southern end, travelling north at a constant speed of 25 ms-. The second train starts at the northern end 40s later, travelling south at a constant speed of 15 ms-. Sketch the two displacement-time graphs on the same set of axes. a b Find the time for which the first train has been moving and the distance the first train has travelled when the trains pass each other.