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Question: Answered & Verified by Expert
Length, width and mass of a rectangular plate are \( \ell, \mathrm{b} \) and \( \mathrm{m} \) respectively. The radius of
gyration about the axis passing through centre and perpendicular to the plane is :
PhysicsRotational MotionJEE Main
Options:
  • A \( \sqrt{\frac{\ell^{2}+\mathrm{b}^{2}}{2}} \)
  • B \( \sqrt{\frac{\ell^{2}+\mathrm{b}^{2}}{8}} \)
  • C \( \sqrt{\frac{\ell^{2}+\mathrm{b}^{2}}{12}} \)
  • D \( \sqrt{\frac{\ell^{2}+b^{3}}{12}} \)
Solution:
2178 Upvotes Verified Answer
The correct answer is: \( \sqrt{\frac{\ell^{2}+\mathrm{b}^{2}}{12}} \)

Moment of inertia of a rectangular plate about an axis passing through its centre and perpendicular to the plane is given by

I=ml2+b212              ....1

As radius of gyration k is given by using the expression

I=mk2

So, k=Im

k=l2+b212.

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