dont know if this is to late but you needto do is get a piece of wood, put a weight on it, you will need a weighing device, like what you use to weigh fish,( you know with a hook either end, you have put one hook on a object, then hang the fish on the other hook to see its weight) but instead of using a weight as a guide you can get ones that show force (science lab should have one, you have to do it during break or bunk from scool when you get one) then simply pull the wood by the force meter over different floors such as wood, plastic, glass, sand paper, carpet etc, and write down the amount of force needed to pull a object over different surfaces, you can do it at a few weights aswell. hope you understand it, i done it a while ago, quite simple really, if all fails copy off your mate, but dont forget to change it a bit, or say you worked together on it