The observation that these devices are not isochronous inspired Christiaan Huygens (“HOW-ginz”) to solve the tautochrone problem. The period of these devices depends (10[1])on their (10[1])initial displacement (10[1])and is proportional (10[1])to an elliptic integral of the first kind. A coupled pair of these devices is a classic (10[1])example of a chaotic system. (10[2])When these devices’ equation of motion is linearized with the small angle approximation, 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 (10[1])(“foo-KOH”). For 10 points, what devices consist of a mass (10[1])at the end of a rod? ■END■