The collective behavior of many interacting examples of these systems is described in the Kuramoto model. The expression “mu times the quantity 1 minus x-squared” multiplies x-dot in an ODE describing one of these systems. Long build-ups followed by sudden discharges are characteristic of the “relaxation” type of these systems. Cartwright (10[1])and Littlewood studied a nonlinear one of these systems named for Dutch engineer Balthasar van der Pol. The time evolution of one type of these (10[1])systems traces an ellipse in phase space. The dissipation of one type of these systems is described by their Q-factor. An LC circuit behaves as one of these systems, as it satisfies the generic differential equation, “mx-double-dot equals minus kx.” For 10 points, Hooke’s law describes the “simple harmonic” type of what systems? ■END■