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NEET 2010 (AIPMT, Mains) · Moment of Inertia & Radius of Gyration

Moment of Inertia & Radius of Gyration question from NEET 2010 (AIPMT, Mains)

Q184NEET 2010 · AIPMT · MAINSMedium

Moment of Inertia & Radius of Gyration

From a circular disc of radius R and mass 9M, a small disc of mass M and radius R3\frac{R}{3} is removed concentrically. The moment of inertia of the remaining disc about an axis perpendicular to the plane of the disc and passing through its centre is

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Answer: (a)

  1. Both discs are concentric, so no parallel-axis term.
  2. I=9MR22−M2(R3)2=81MR2−MR218I = \frac{9MR^2}{2} - \frac{M}{2}\left(\frac{R}{3}\right)^2 = \frac{81MR^2 - MR^2}{18}
  3. I=409MR2I = \frac{40}{9}MR^2, so the answer is (a).
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