Two trucks A and B, of masses 6000kg and 4000kg respectively, are connected by a horizontal coupling. An engine pulls the trucks along a straight horizontal track, exerting a constant horizontal force of magnitude X newtons on truck A. The resistance to motion for truck A may be modeled by a constant horizontal force of magnitude 360N; for truck B the resistance may be modeled by a constant horiztonal force of 240N. Given that the tension in the coupling is T newtons and that the acceleration of the trucks is ams^-2, show that T=\frac{2}{5}X, and express a in terms of X.
Given that the trucks are slowing down, obtain an inequality satisfied by X.
The model is changed so that the resistance for truck B is modeled by a constant force of magnitude 200N. The resistance for truck A remains unchanged. For this changed model find the range of possible values of X for which the force in the coupling is compressive (i.e. the force in the coupling acting on B is directed from A to B).
How is the third part done? I did the rest