Im doing a prac for school that we have to create ourselves. My groups prac goes along the line of a train pulling two carriages. Our train is a LEGO NXT unit that runs at a constant velocity, no acceleration. We will have two force gauges between each carriage and the carriage and the train and test how the tension changes as we increase the mass and run them up a incline. We want to compare the real world figures to how the tension would be as calculated on paper. Is there any equations that apply to no acceleration, constant velocity for calculating the tension? Thanks.