Friction coefficient on a rotating cylinder [mechanics]

albatross84

1. 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 [Broken]

2. Homework Equations
F=ma
Ff=uma
etc...

3. 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.
1. Homework Statement

2. Homework Equations

3. The Attempt at a Solution
1. Homework Statement

2. Homework Equations

3. The Attempt at a Solution

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tiny-tim

Homework Helper
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

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