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Question: Answered & Verified by Expert
The ratio of the radii of gyration of a circular disc about a tangential axis in the plane of the disc and of a circular ring of the same radius about a tangential axis in the plane of the ring is
PhysicsRotational MotionJEE Main
Options:
  • A $1: \sqrt{2}$
  • B $1: 3$
  • C $2: 1$
  • D $\sqrt{5}: \sqrt{6}$
Solution:
1120 Upvotes Verified Answer
The correct answer is: $\sqrt{5}: \sqrt{6}$



$\begin{aligned} & \mathrm{I}_{\text {disk }}=\frac{5}{4} \mathrm{MR}^2=\mathrm{MK}_{\text {disk }}^2 \\ & \mathrm{I}_{\text {ring }}=\frac{3}{2} \mathrm{MR}^2=\mathrm{MK}_{\text {ring }}^2 \\ & =\frac{\mathrm{K}_{\text {disk }}}{\mathrm{K}_{\text {ring }}}=\sqrt{\frac{\overline{5}}{6}}\end{aligned}$

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