1. The problem statement, all variables and given/known data first of all- yes,i looked in to similar topics,did not succeed :( My problem : The objects slides down on a plane which located 45degrees with respect to surface. It slides s=0.36m down, it reaches v=2m/s. I have to calculate the coefficient of friction. 2. Relevant equations 3. The attempt at a solution There is image( sorry for some reason, i could not upload it directly to here) http://postimg.org/image/uof2i65zv/ [Broken] So the friction coef. F_friction=(mu)*F_reaction -> (mu)=F_f/F_r From image above, its easy to see,that tan(alpha)=mu,so it seems too easy. And what for i need s and v values? I suppose it could be because i just calculated the static friction ,not the dynamic,yes? If i should calculate the dynamic one,could someone help ,please?