The observation that these devices are not isochronous inspired Christiaan Huygens (“HOW-ginz”) to solve the tautochrone problem. (-5[1])The period of these devices depends on their initial displacement and is proportional to an elliptic integral of the (10[1])first kind. (10[1])A coupled pair of these (10[1])devices is a (10[1])classic example (10[2])of a (10[1])chaotic system. (10[2])When these devices’ equation of motion is linearized with the small angle approximation, (10[1])they can be approximated as harmonic oscillators whose frequency is the square root of little g over L. The Earth’s rotation causes the precession of a type of these devices named for Léon Foucault (“foo-KOH”). For 10 points, what devices consist of a mass at the end of a rod? ■END■ (10[2])