A reversible one of these objects uses the mathematical expression [read slowly] “four pi squared D over T squared” as an approximation in an experimental setup proposed by Henry Kater. An application to one of these objects illustrates the Berry phase by getting the Hannay angle (10[1])through decomposition. Calculating the Lagrangian of one system involving these objects contains the term (*) [read slowly] “3 cosine theta-sub-one minus cosine theta-sub-two”; that dynamical system involves (10[1])two of these objects coupled together. In introductory physics classes, using the small angle approximation reduces the motion of these systems to simple harmonic (10[1])motion. For 10 points, name these swaying objects that usually consist of a mass attached to the end of a string or a rod. ■END■