Graphical representation of F(v)≔ − γ|v − w|(v − w)+a and local portrait of the speed dynamics around the stable equilibrium of the EDBM in the cases a < 0 and a > 0. The arrows define the positive sense of time for the evolution of v(t). Solid and dashed lines correspond to F > 0 (graph above the line, arrow pointing to the right) and F < 0 (graph below the line, arrow pointing to the left), respectively.