ABSTRACT
Most of the introductory textbooks on physics or mechanics contain a section on friction. Usually, fewer than one or two lectures are devoted to explaining how to treat such problems in high school science class or undergraduate college courses, and a few homework questions may be assigned. In such cursory treatments, it is customary to de ne the static and kinetic friction coef cients, to show how free-body diagrams and force polygons (sometimes called string polygons) can be constructed to account for friction forces, and to show how the student may approach macroscopic friction problems when the friction coef cient either is extracted from tables or can be “back-calculated” from the conditions of the problem. Sometimes simple explanations of surface roughness-based origins for friction are given. Usually little or nothing is said about the metallurgical aspects of friction, the role or nature of lubricating lms, or the possibility of time-dependent frictional transitions. Although such introductory approaches are useful, they can be misleading since they do not prepare students for the complexities of frictional behavior in real-world, practical situations.
