Demonstration of coupled oscillations.
A Wilberforce pendulum consists of a plumb bob which hangs from
a spring. The Wilberforce pendulum has four modes of oscillation:
translational (vertical), torsional, and two pendula modes. The bob's
moment of inertia can be tuned to demonstrate energy transfer between
the translational and torsional modes. The moment of inertia should
be adjusted so that the rotational period is approximately equal to
the translational period. When the resulting beat frequency is is
much smaller than the frequency of the two normal modes energy exchange
between the two degrees of freedom is easily observed.
