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Non-Linear pendulum

• To: mathgroup at smc.vnet.net
• Subject: [mg104874] Non-Linear pendulum
• From: Allamarein <matteo.diplomacy at gmail.com>
• Date: Thu, 12 Nov 2009 06:04:33 -0500 (EST)

I'm getting to know Mathematica. I want to compile a code to see the
non-linear pendulum behavior.

pendulum= {Line[{{0, 0}, {0, -1}}], Circle[{0, -1.3}, 0.3]};
l = 20;
g = 9.81;
s = NDSolve[
   { \[Theta]''[t] == -g /l Sin[\[Theta][t]],
    \[Theta][0] == Pi/2,
    \[Theta]'[0] == 0}, \[Theta],
   {t, 0, 30}];
Animate[
 Graphics[Rotate[pendulum, \[Theta[]t], {0, 0}],
  PlotRange -> {{-2, 2}, {0, -2}}],
 {t, 0, 30}, AnimationRunning -> False]

This code doesn't work. I realized my error is in Rotate argument. If
I change this line with:

Graphics[Rotate[pendulum, Sin[t], {0, 0}]

code runs, but it's not the result (obviously).
How can I correct my code, to see the pendulum oscillates with \[Theta]
[t] law?

• Follow-Ups:
  • Re: Non-Linear pendulum
    • From: Mark McClure <mcmcclur@unca.edu>