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NEET 2008 (AIPMT) · Moment of Inertia & Radius of Gyration

Moment of Inertia & Radius of Gyration question from NEET 2008 (AIPMT)

Q188NEET 2008 · AIPMTMedium

Moment of Inertia & Radius of Gyration

A thin rod of length L and mass M is bent at its midpoint into two halves so that the angle between them is 90°. The moment of inertia of the bent rod about an axis passing through the bending point and perpendicular to the plane defined by the two halves of the rod is

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Answer: (d)

  1. Each half: mass M2\frac{M}{2}, length L2\frac{L}{2}, rotating about its end (the bend point).
  2. Each half: 13⋅M2⋅L24=ML224\frac{1}{3}\cdot\frac{M}{2}\cdot\frac{L^2}{4} = \frac{ML^2}{24}. The angle between halves does not matter.
  3. I=2×ML224=ML212I = 2 \times \frac{ML^2}{24} = \frac{ML^2}{12}
  4. So the answer is (d) ML212\frac{ML^2}{12}.
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