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NEET 2004
Exam
NEET
Year
2004
Subject
Physics
Chapter
Rotational Motion

NEET 2004 · Physics · Rotational Motion

An round disc of moment of inertia I_2 about its axis perpendicular...

An round disc of moment of inertia I2I_2 about its axis perpendicular to its plane and passing through its centre is placed over another disc of moment of inertia I1\mathrm{I}_1 rotating with an angular velocity ω\omega about the same axis. The final angular velocity of the combination of discs is:

Options

  1. AI2ωI2+I2\frac{I_2 \omega}{I_2+I_2}
  2. Bω\omega
  3. CI1ωI1+I2\frac{I_1 \omega}{I_1+I_2}
  4. D(I1+I2)ωI1\frac{\left(I_1+I_2\right) \omega}{I_1}

Correct answer

C. I1ωI1+I2\frac{I_1 \omega}{I_1+I_2}

Step-by-step solution

From law of conservation of angular momentum we have:I1ω1=(I1+I2)ω2∴ω2=I1ω1(I1+I2)=I1ωI1+I2\begin{aligned}& I_1 \omega_1=\left(I_1+I_2\right) \omega_2 \\ & \therefore \quad \omega_2=\frac{I_1 \omega_1}{\left(I_1+I_2\right)}=\frac{I_1 \omega}{I_1+I_2}\\ & \end{aligned}
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