What is the relationship between a ball rolling down a slope (ramp) and its average velocity. I know we are supposed to use: v^2 = ut + at/2 and F = mgsin(degree). But assume initial velocity is zero. Also if I do an experiment and I get results (make a graph between average velocity and cosine or sine of angle) how can I find the frictional force found within the slope? I'll know there is an error (friction) as the graph is linear but nor propotional. Thanks!