An object of mass m is suspended at the end of a massless wire of length L and area of cross-section,

Question:

An object of mass $m$ is suspended at the end of a massless wire of length $L$ and area of cross-section, $A$. Young modulus of the material of the wire is $Y$. If the mass is pulled down slightly its frequency of oscillation along the vertical direction is:

  1. $f=\frac{1}{2 \pi} \sqrt{\frac{m L}{Y A}}$

  2. $f=\frac{1}{2 \pi} \sqrt{\frac{Y A}{m L}}$

  3. $f=\frac{1}{2 \pi} \sqrt{\frac{m A}{Y L}}$

  4. $f=\frac{1}{2 \pi} \sqrt{\frac{Y L}{m A}}$


Correct Option: 1

Solution:

(1) An elastic wire can be treated as a spring and its spring constant.

$k=\frac{Y A}{L}$            $\left[\because Y=\frac{F}{A} / \frac{\Delta l}{l_{0}}\right]$

Frequency of oscillation,

$f=\frac{1}{2 \pi} \sqrt{\frac{k}{m}}=\frac{1}{2 \pi} \sqrt{\frac{Y A}{m L}}$

 

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