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Rotational Motion question

2022 · 26 Jul · Shift 2 · Q59
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  5. /2022 · 26 Jul · Shift 2 · Q59

Rotational Motion question

2022 · 26 Jul · Shift 2 · Q59

JEE MainPhysicsRotational MotionNumerical+4 / −1
The radius of gyration of a cylindrical rod about an axis of rotation perpendicular to its length and passing through the center will be ‾m\underline{\hspace{2cm}}\mathrm{m}​m. Given, the length of the rod is 103 m10 \sqrt{3} \mathrm{~m}103​ m.
Numerical answer
View written solutionFree

Correct answer: 5

  1. Formula for radius of gyration

For a thin rod of length LLL, about an axis perpendicular to its length and passing through its center, the moment of inertia is

I=112ML2I = \frac{1}{12}ML^2I=121​ML2

Radius of gyration kkk is defined by

I=Mk2I = Mk^2I=Mk2

So,

Mk2=112ML2Mk^2 = \frac{1}{12}ML^2Mk2=121​ML2

k2=L212k^2 = \frac{L^2}{12}k2=12L2​

k=L12=L23k = \frac{L}{\sqrt{12}} = \frac{L}{2\sqrt{3}}k=12​L​=23​L​

  1. Substitute the given length

Given,

L=103 mL = 10\sqrt{3}\,\text{m}L=103​m

Therefore,

k=10323=102=5 mk = \frac{10\sqrt{3}}{2\sqrt{3}} = \frac{10}{2} = 5\,\text{m}k=23​103​​=210​=5m

  1. Final answer

5\boxed{5}5​

  1. Comparison with stored answer

Stored correct answer = 555

My derived answer is also 555, so they agree.

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