The Pendulum - Demo 4

Driven Damped Pendulum - large amplitude oscillations

Now increase the driving strength to 0.9 (we will not bother to show the transient).

The "power spectrum" now shows more harmonics:

(You should increase the speed and run the iteration to refine the spectrum by averaging over a longer time sequence.) The maximum frequency set by the Nyquist relationship /(dt*Interval) has been changed to show more harmonics. Some "side bands" appear on the peaks that do not appear to be harmonically related to the fundmental frequency. These are actually "aliasing" artifacts - higher harmonics are folded back into the Nyquist frequency range (see chapter 6). If you change dt to change the maximum frequency, you can study this phenomenon.

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Last modified Wednesday, November 24, 1999
Michael Cross