JEE Mains · Physics · STD 11 - 6. system of particles and rotational motion
A circular disc of mass \(M\) and radius \(R\) is rotating about its axis with angular speed \(\omega_{1}\) If another stationary disc having radius \(\frac{ R }{2}\) and same mass \(M\) is dropped co-axially on to the rotating disc. Gradually both discs attain constant angular speed \(\omega_{2}\). The energy lost in the process is \(p \%\) of the initial energy. Value of \(p\) is
- A \(25\)
- B \(27\)
- C \(20\)
- D \(15\)
Answer & Solution
Correct Answer
(C) \(20\)
Step-by-step Solution
Detailed explanation
Let moment of inertia of bigger disc is \(I =\frac{ MR ^{2}}{2}\) \(\Rightarrow\) \(MOI\) of small disc \(I_{2}=\frac{M\left(\frac{R}{2}\right)^{2}}{2}=\frac{I}{4}\) by angular momentum conservation…
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