Friction coefficient on a rotating cylinder [mechanics]

[albatross84]

Homework Statement

Here is a picture of the problem I am trying to solve in a book. The problem I am having trouble with is #4 (the solution is provided in the brackets below the question -> 0.432)
http://img15.imageshack.us/img15/241/questiona.jpg

Homework Equations

F=ma
Ff=uma
etc...

The Attempt at a Solution

I have tried accounting for all the possible cases (including all free body diagrams I could think of) - Fg, and two Fn's and Ff's on both sides of contact (as well as individually). I have drawn all of my Fn's and Fg's through the center of gravity, which I am not entirely sure about. All of my attempts have so far given me a different number from the suggested solution.
In particular, I was hoping someone could help me out with the present forces and how they are drawn on the free body diagram (center of gravity?). Thanks.

 

[tiny-tim]

Welcome to PF!

Hi albatross84! Welcome to PF!

… I have drawn all of my Fn's and Fg's through the center of gravity, which I am not entirely sure about …

Yes, you're right not to be sure …

reaction forces always go through the point of contact (so in this case they'll also go though C) …

only the weight goes through the centre of mass