1.5 W -1.5 -1.0 -0.5 0.5 0.5 1.0 1.5 Fig. 1: The graph of f Assume that a point mass moves according to mx + cx + f (x) = 0, where c > 0. (a) What are the physical interpretations of m, c, f above? (b) Write down the first-order differential equation for the solution curves in the phase plane. (c) Assuming that of has the shape in Fig. 1, sketch the isoclines.