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?(adsbygoogle = window.adsbygoogle || []).push({});

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!

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Forces/coefficient of friction

**Physics Forums | Science Articles, Homework Help, Discussion**