JEE Mains · Physics · STD 11 - 6. system of particles and rotational motion
A thin 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 angular velocity \(\omega\). If another disc of same dimensions but of mass \(\mathrm{M} / 2\) is placed gently on the first disc co-axially, then the new angular velocity of the system is _______.
- A \(\frac{4}{5} \omega\)
- B \(\frac{5}{4} \omega\)
- C \(\frac{2}{3} \omega\)
- D \(\frac{3}{2} \omega\)
Answer & Solution
Correct Answer
(C) \(\frac{2}{3} \omega\)
Step-by-step Solution
Detailed explanation
\(\mathrm{I}_1 \omega=\mathrm{I}_2 \omega_2\) \(\frac{\mathrm{MR}^2}{2} \omega=\frac{3}{2}\left(\frac{\mathrm{MR}^2}{2}\right) \omega_2\) \(\omega_2=\frac{2}{3} \omega\)
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