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NEET 2008
Exam
NEET
Year
2008
Subject
Physics
Chapter
Rotational Motion

NEET 2008 · Physics · Rotational Motion

A thin rod of length L and mass M is bent at its midpoint into two...

A thin rod of length LL and mass MM is bent at its midpoint into two halves so that the angle between them is 90∘90^{\circ}. 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 isA 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

Options

  1. AML224\frac{M L^2}{24}
  2. BML212\frac{M L^2}{12}
  3. CML26\frac{M L^2}{6}
  4. D2ML224\frac{\sqrt{2} M L^2}{24}

Correct answer

B. ML212\frac{M L^2}{12}

Step-by-step solution

Since rod is bent at the middle, so each part of it will have same length (L2)\left(\frac{L}{2}\right) and mass \left(\frac{M}{2}\right)asshown.<imgsrc="https://cdn−question−pool.getmarks.app/pyq/neet/WH3QEFan67DSP8e3xFk94x6sEVaHjMCJ9aQ2PyXSzc.original.fullsize.png">Momentofinertiaofeachpartthroughitsoneendas shown. <img src="https://cdn-question-pool.Quantrex.app/pyq/neet/WH3QEFan67DSP8e3xFk94x6sEVaHjMCJ9aQ2PyX_Szc.original.fullsize.png"> Moment of inertia of each part through its one end=\frac{1}{3}\left(\frac{M}{2}\right)(L2)2\left(\frac{L}{2}\right)^2 Hence, net moment of inertia through its middle point OO is I=13(M2)(L2)2+13(M2)(L2)2=13[ML28+ML28]=ML212\begin{aligned} I & =\frac{1}{3}\left(\frac{M}{2}\right)\left(\frac{L}{2}\right)^2+\frac{1}{3}\left(\frac{M}{2}\right)\left(\frac{L}{2}\right)^2 \\ & =\frac{1}{3}\left[\frac{M L^2}{8}+\frac{M L^2}{8}\right]=\frac{M L^2}{12} \end{aligned}
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