A truck of mass 5kg is pulling a smaller truck of mass 2kg up a slope inclined at 10degrees to the horizontal. The trucks are joined together by a light, rigid coupling. The 5kg truck has a resistance of 8N and the smaller truck has a resistance of 6N. The string pulling the trucks is parallel to the horizontal and has a tension of 43N. The two trucks are accerelerating at 2.5ms-2. What is the tension in the coupling?
Also, show that the coupling remains in tension whatever the tension in the string is.
The Attempt at a Solution
I've drawn a diagram but I am struggling most on which way the tension in the coupling would be so whether to take it away or add it in the Force part of the equation. I've only done the equation for the first truck, but not sure whether it is right:
Tension in string- Resistance- Weight component-Tension in coupling= ma
I really have no idea for the second part.
Any help at all would be greatly appreciated.