In order to calculate the trailer acceleration, we can use the second law of Newton:
[tex]\sum ^{}_{}F=m\cdot a[/tex]Since the frictional force is against the applied force, the net force is the difference between these forces.
So we have:
[tex]\begin{gathered} 7310-1820=2960\cdot a \\ 5490=2960\cdot a \\ a=\frac{5490}{2960} \\ a=1.855\text{ m/s2} \end{gathered}[/tex]Therefore the trailer acceleration is 1.855 m/s².