Simulació basada en la física de dos pèndols impulsats que comencen quasi de manera idèntica; així es demostra la sensibilitat a les condicions inicials dels sistemes caòtics. Es veu com un sol un pèndol al principi, però esperant un minut es veu que els dos pèndols divergeixen en el seu comportament.
Clique en la pestanya "Simulador" per a accedir a paràmetres com: diferència d'angle inicial, unitat amplitud, freqüència, massa, gravetat i amortiment. Pots arrossegar el pèndol amb el teu ratolí per a canviar la posició inicial.
The pendulums are continuously driven by an external torque force that varies
between twisting clockwise and counterclockwise. This torque force is represented by
the curved arrow, the length of the arrow corresponds to the strength of the force.

graph of angular velocity vs. angle for two chaotic pendulums
These are two independent pendulum simulations running simultaneously. They start
with almost identical initial conditions, but just slightly different starting angles
(the difference is the angle difference parameter). Running for several
minutes produces the graph shown at left.
You will notice that the pendulums stay in sync for a while, then drift slightly
apart, and then are soon completely different in their behavior. This is an example of
sensitivity to initial conditions which is a hallmark of
chaotic systems.
This is also known as the
Butterfly Effect whereby a
butterfly flapping its wings in North America could cause a storm to occur in South
America.
The angle difference parameter specifies the difference
between the start angle of the two pendulums. Try different values for the starting
angle difference, and measure how much time it takes for the pendulums to diverge
significantly. If you make a graph of this (difference in starting angle vs time to
divergence), is it a linear or exponential curve? Is this different to how a linear
system would respond?
For the math behind the simulation see the page about the
Chaotic Driven Pendulum; this is the same
simulation as that one, except here there are two pendulums.
Also available are:
open source code,
documentation and a
simple-compiled version
which is more customizable.