Question

two circular discs have masses in the ratio of 2 :1 and diameters in the ratio of 1 : 2. if they rotate with the same angular momentum about a fixed axis passing through the center and perpendicular to the disk, then the ratio of their angular speeds is:
(A) 1
(B) 2
(C) 4
(D) 8

Answer 1

Answer:

consider the problem

Moment of inertia of the ring is given by

I=mr2

Where m is the mass of the ring and r is the radius of the ring in terms of diameter

I=4md2

For first ring

I1=4m1d12I2=4m2d22I2I1=12d2d1=12

I2I1=4m2d224m