While dry Coulombic friction is an elementary topic in any standard introductory course in mechanics, the critical distinction between the kinetic and static friction forces is something that is both hard to teach and to learn.
In this paper, I describe a geometric model of static friction that may help introductory students to both understand and apply the Coulomb static friction approximation….
Read more at http://arxiv.org/pdf/1507.04015v1.pdf