Deterministic chaos in the elastic pendulum: a simple laboratory for nonlinear dynamics

The chaotic motion of the elastic pendulum is studied by means of four indicators, the Poincare section, the maximum Lyapunov exponent, the correlation function, and the power spectrum. It is shown that for very low and very large energies the motion is regular while it is very irregular for intermediate energies. Analytical considerations and graphical representations concerning the applicability of KAM theorem are also presented. This system and the type of description used are very suitable to introduce undergraduate students to nonlinear dynamics