Is there a link someone can provide that has a good tutorial on friction coefficient formulas and when to apply them. I seem to be having problems with this topic. Everyone knows the old M1 and M2 connected by a string and pully question. That is on a level surface. But if the surface is tilted backward so the corner now makes a 53 degree angle instead of 90 how do I go about finding the acceleration. Is it the same way as before but with something else added into it besides the kinetic friction? I have been working on physics all day and my brain is about to boil over. Thank you.