Question

A thin uniform circular disc of mass M and radius r is rotating in a horizontal plane about an axis passing through its centre and perpendicular to its plane with an angular velocity $\omega .$ Another disc of the same dimensions but of mass M/4 is placed gently on the first disc co-axially. show that angular velocity of the system is $4\omega /5.$

• A. $\frac{5\omega }{4}$
• B. $\frac{9\omega }{5}$
• C. $\frac{5\omega }{8}$
• D. $\frac{4\omega }{5}$

Answer 1

The correct option is D $\frac{4\omega }{5}$

Hence, option $\left(D\right)$ is correct answer.