A box of canned goods slides down a ramp from street level into the basement of a grocery store with acceleration 0.65 m/s2 directed down the ramp. The ramp makes an angle of 35 degrees with the horizontal. What is the coefficient of kinetic friction between the box and the ramp? I have been trying to figure this out for a while. Heh. So far I drew my picture. One thing I am confused about is what direction friction is in. I thought that since the box is sliding downward with a force, then the frictional force is up and opposite of that sliding force. I might have this mixed up. I dont know if there is a force pushing it down. Then I broke it up into X component forces: Fa - friction (making the downward direction positive) + Wx = ma Then I became confused about the Fa and wondered if it even belongs. So then: -f + wx = ma -Mu(mg) + mgsin35 = ma (then cancel out the masses) Mu(g) + gsin35 = a Mu(g) = a - gsin35 Mu = a - sin35 I have done something wrong. If anyone can help me figure this out, I would really appreciate it. I have tried my best!