A horizontal disc revolves about a vertical axis at the rate of 100 rev/sec. A small piece of wax of 10 gm. falls on the disc and sticks at a distance of 9 cm from the axis. If the disc now revolves at the rate of 90 rev / sec, calculate the moment of inertia of the disc.
7920 gm.cm2
7290 gm.cm2
8920 gm.cm2
8290 gm.cm2