Determine the smallest coefficient of friction

[blackandyello]

Homework Statement

The horizontal force P acts on the rim of the homogeneous cylinder of radius R and weight W. Determine the smallest coefficient of static friction that enables the cylinder to start rolling up the 30◦ incline.

Homework Equations

*depends on the fbd. refer below

The Attempt at a Solution

since its being ask for the coefficient of friction, which FBD would be correct? should it be a vertical normal force with friction force going on left, or should it be the normal force facing perpendicularly the 30 degree include while the friction is along the 30 degree line also. which is the proper fbd? tnx

 

[Astronuc]

Friction acts tangentially to the radius of a cylinder, and the force of friction is proportional to the normal force on a surface.