1. The problem statement, all variables and given/known data A truck that has a mass of 5kg is being pulled up a slope by a string. The truck is also pulling another truck of mass 2kg up the slope with a rigid coupling inbetween the trucks. Ths slope is inclined at 10 degrees to the horizontal. The 5kg truck has a resistance of 8N and the smaller truck a resistance of 6N. Show that the coupling remains in tension, regardless of the tension in the string, whilst the trucks are moving up the slope. 2. Relevant equations I've been told that this is true: gsin10+6/2 > gsin10+8/5 3. The attempt at a solution I understand why the smaller truck has got to be greater. But I don't understand why the masses are divided on the equaiton. I thought that it would be 2gsin10 etc. but that doesn't work. Any help at all would be greatly appreciated.