Two railway trucks \(A\) and \(B\), of masses 10000 kg and 7000 kg respectively, are moving towards each other along a horizontal straight track. The trucks collide, and in the collision \(A\) exerts an impulse on \(B\) of magnitude 84000 Ns. Immediately after the collision, the trucks move together with speed \(10 \mathrm {~ms} ^ { - 1 }\). Modelling the trucks as particles,
find the speed of each truck immediately before the collision.
When the trucks are moving together along the track, the coefficient of friction between them and the track is 0.15 . Assuming that no other resisting forces act on the trucks, calculate
the magnitude of the resisting force on the trucks,
the time taken after the collision for the trucks to come to rest.