A chain of masses joined by springs, plucked into its slowest mode. With linear springs the energy stays put. Add a little nonlinearity and it should spread evenly across all modes — yet instead it wanders and then almost perfectly returns. Pick a force law and watch.
Force law · spring force vs. stretch δ
View
Simulation
time t 0
Energy in each normal mode — % of total1234
nonlinearlinear
−1+1displacement
3D needs WebGL, which isn't available here — showing the 2D view instead.