Comment: collision with friction; part B: Poisson’s and Stronge’s hypotheses

For planar oblique collision with friction that opposes sliding at the contact point, this comment compares calculations of terminal relative velocity and energy dissipation obtained using the kinematic (Newton), kinetic (Poisson) and energetic (Stronge) definitions for coefficient of restitution. The kinematic and kinetic definitions yield results which are energetically inconsistent for some initial velocities when sliding stops or changes direction before separation. If initial sliding does not come to a stop before separation, the three definitions are equivalent. In general, only the energetic coefficient of restitution e _S satisfies e _S≤1.