Abstract
In this paper, I argue that the correct mathematical expression for the work done by the force of kinetic friction depends on how the body who is subject to friction is being modelled: as a particle or as a system of particles. I argue that both alternatives are valid, and that the choice of one of them depends on the type of information that interests us in the problem. In the second case, however, the very expression “work done by the force of kinetic friction” needs to be modified.
Keywords:
force of kinetic friction; work; work - kinetic energy theorems; systems of particles; modelling
