1. The problem statement, all variables and given/known data mg sin θ/mg cos θ = μ (coefficient of friction) sinθ/cosθ = tanθ 3. The attempt at a solution then does μ = tanθ/mg (which is what my teacher said, although i'm not sure i understand) OR is the above equation simplified so that μ = tanθ? :uhh: thanks for your help - and any other information on finding the frictional force, acceleration etc. would be good too. I read that the coefficient of friction is always a constant. but is this still true if the acceleration increases? i should make things clearer: i have some data from an experiment where a trolley is released from the top of a ramp, but the height is altered each time. (there's also a light gate involved too, but i'm not stuck on that yet - although any passing info would definitely be useful, thanks) edit: also, I plotted an acceleration v. sinθ (the angle of the ramp) graph, and expected that the gradient would be 9.81 , and that the intercept would either be 0, or below (due to frictional forces). instead, the intercept was actually a bit above 0 and the gradient wasn't 9.81 (but close). Should i bother trying to explain this..as i don't really know how to, or is just some discrepancy when i plotted the graph using excel?