torsional pendulum

torsional pendulum

[′tȯr·shən·əl ′pen·jə·ləm] (mechanics) A device consisting of a disk or other body of large moment of inertia mounted on one end of a torsionally flexible elastic rod whose other end is held fixed; if the disk is twisted and released, it will undergo simple harmonic motion, provided the torque in the rod is proportional to the angle of twist. Also known as torsion pendulum.