Agrandfather clock has a pendulum that consists of a thin brass disk of radius r = 13.62 cm and mass 1.199 kg that is attached to a long thin rod of negligible mass. the pendulum swings freely about an axis perpendicular to the rod and through the end of the rod opposite the disk, as shown in fig. 15-54. if the pendulum is to have a period of 1.583 s for small oscillations at a place where g = 9.846 m/s2, what must be the rod length l (in m)?