A uniform disk of radius r = 120 mm is welded at its center to two elastic rods of equal l...

A uniform disk of radius r = 120 mm is welded at its center to two elastic rods of equal length with fixed ends at A and B. Knowing that the disk rotates through an 8° angle when a 500-mN• m couple is applied to the disk and that it oscillates with a period of 1.3 s when the couple is removed, determine (a)the mass of the disk, (b)the period of vibration if one of the rods is removed.