The moment of inertia of a uniform rod about a perpendicular axis passing through one of its ends is \(\mathrm{I}_{1}\). The same rod is bent in to a ring and its moment of inertia about a diameter is \(\mathrm{I}_{2}\), Then \(\left[\mathrm{I}_{1} / \mathrm{I}_{2}\right]\) is. \(\\{\mathrm{A}\\}\left(\pi^{2} / 3\right)\) \(\\{B\\}\left(4 \pi^{2} / 3\right)\) \(\\{\mathrm{C}\\}\left(8 \pi^{2} / 3\right)\) \(\\{\mathrm{D}\\}\left(16 \pi^{2} / 3\right)\)

Short Answer

Expert verified
The short answer for the given problem is: \(\frac{I_1}{I_2} = \frac{4\pi^2}{3}\), which corresponds to option B.

Step by step solution

01

Find the Moment of Inertia of the Rod

For a uniform rod of mass \(m\) and length \(L\), the moment of inertia (\(I_1\)) about a perpendicular axis passing through one end is given by: \(I_1 = \frac{1}{3}mL^2\) #Step 2: Moment of Inertia of Ring#
02

Find the Moment of Inertia of the Ring

To find the moment of inertia of the same rod bent into a ring, first, determine the radius (\(R\)) of the resulting ring by dividing the length of the rod by the circumference of the circle: \(R = \frac{L}{2\pi}\) Now, the moment of inertia (\(I_2\)) for a uniform ring of mass \(m\) and radius \(R\) about a diameter is given by: \(I_2 = mR^2\) #Step 3: Substitute the expression for R into \(I_2\)#
03

Replace R with the expression found in Step 2

Use \(R=\frac{L}{2\pi}\) to replace R with an expression involving L in the formula for \(I_2\): \(I_2 = m\left(\frac{L}{2\pi}\right)^2\) Simplify this expression: \(I_2 = \frac{mL^2}{4\pi^2}\) #Step 4: Find the ratio \(\frac{I_1}{I_2}\)#
04

Calculate the ratio of \(I_1\) and \(I_2\)

Divide \(I_1\) by \(I_2\): \(\frac{I_1}{I_2} = \frac{\frac{1}{3}mL^2}{\frac{mL^2}{4\pi^2}}\) Now, cancel \(mL^2\) from the numerator and the denominator: \(\frac{I_1}{I_2} = \frac{1/3}{1/(4\pi^2)} = \frac{1}{3} \cdot (4\pi^2) = \frac{4\pi^2}{3}\) Comparing this result with the given options, we can see that the correct answer is: \\({\mathrm{B}}\\) \(\left(4 \pi^{2} / 3\right)\)

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