Initial-amplitude dependence in weakly damped oscillators
  A pedagogically instructive experimental procedure is suggested for distinguishing between different damping terms in a weakly damped oscillator, which highclights the connection between non-linear damping and initial-amplitude dependence. The most common damping terms such as contact friction, air resistance, viscous drag, and electromagnetic damping have velocity dependences of the form constant, v, or v^2. The corresponding energy dependences of the form \sqrt{E}, E, or E\sqrt{E} in the energy loss equation give rise to characteristic dependence of the amplitude decay slope on the initial amplitude. 
Avinash Singh