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[Phys-L] Again: Re: [Phys-l] accurate numerical solution of equations of motion



I’ve been using the leapfrog method described in Eisberg and Lerner, I thought successfully. Until I tried testing the accuracy of a very simple harmonic oscillator by fitting and then having the fit find the residuals. The residuals increase with time! A quick read of Cromer explains and suggests I switch to the last point method. However, my understanding of this conversation is I will have error when I introduce drive and dissipation. I’ve already run these, but only for a few seconds of a one second pendulum. Please assist.

Note: the error(s) I found after 80 periods of my one second harmonic oscillator with an amplitude of 0.1 radian are ~ + & - 2e-6 radian [time step = 2E-3s; difference between a sinusoidal fit and the simulation]

bc


On 2009, Nov 04, , at 08:41, John Denker <jsd@av8n.com> wrote: