This page describes work done by Mohammad Rafat, Mike Wheatland,
and Tim Bedding.
A paper on the work has been
published in the American Journal of Physics (Rafat, Wheatland and Bedding
2009). The article
is available here.
Intermediate energy
At higher energy, more sets of initial conditions produce chaos.
The animation and
Poincare section below are for E = 8. A large part of the
Poincare section is filled with scattered points. However, some
regular behaviour (corresponding to curves and points in the section)
is also observed, and the animation provides an example of regular
behaviour. The animation indicates that the pendulum is not
particularly energetic: in fact there is insufficient
energy for the lower plate to rotate completely (this requires
energies larger than E = 17.0, approximately).
The motion is almost completely chaotic around E = 20
(the Poincare section is almost completely filled with points, although
it is notable that the slow mode survives).
The animation and Poincare section below
illustrate this case. The lower plate now has sufficient energy to rotate
completely, but the upper plate cannot rotate completely (this happens
for energies larger than E = 37.9, approximately).
.
The motion is completely chaotic around E = 35 (the Poincare section
is filled with dots, within the allowed region). The upper plate still has
insufficient energy to rotate completely.
The animation and Poincare section below illustrate this case.
Both plates can rotate completely when the energy is larger than about
E = 54.9. At somewhat higher energy regular behaviour begins
to reappear in the Poincare section.
The animation and Poincare section below illustrate the case
E = 80.
The dynamics of the pendulum at low energy is described
here. The dynamics of the pendulum at high
energy is described here. A large
gallery of Poincare sections is provided
here.
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