4 Two trucks, A and B, each of mass 10000 kg , are pulled along a straight, horizontal track by a constant, horizontal force of \(P \mathrm {~N}\). The coupling between the trucks is light and horizontal. This situation and the resistances to motion of the trucks are shown in Fig. 4.
\begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{bf477f61-9f8f-418a-86d8-392bc30323b1-2_198_948_1454_592}
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\caption{Fig. 4}
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The acceleration of the system is \(0.2 \mathrm {~ms} ^ { 2 }\) in the direction of the pulling force of magnitude \(P\).
- Calculate the value of \(P\).
Truck A is now subjected to an extra resistive force of 2000 N while \(P\) does not change.
- Calculate the new acceleration of the trucks.
- Calculate the force in the coupling between the trucks.