Attaching two of these devices end to end creates a chaotic device whose trajectories trace out part
Attaching two of these devices end to end creates a chaotic device whose trajectories trace out part of a topological torus. The generic equation of motion for these devices is "theta-double-dot equals negative k times sine theta", assuming there are no extended masses present, as in the "compound" type of this device. One type of these devices picks up a geometric phase as the Earth rotates, causing it to precess; that type is named for Foucault. The period of these devices equals "2 pi times root (length over small g)". For 10 points, name this simple device consisting of a weight suspended from a string, which exhibit approximate simple harmonic motion.
Attaching two of these devices end to end creates a chaotic device whose trajectories trace out part of a topological torus.
pendulum [accept simple pendulum; accept Foucault's pendulum; accept double pendulum] 