A stationary tuning fork is in resonance with an air column in a...

A stationary tuning fork is in resonance with an air column in a pipe. If the tuning fork is moved with a speed of

2m{s}^{- 1}

in front of the open end of the pipe and parallel to it, the length of the pipe should be changed for the resonance to occur with the moving tuning fork. If the speed of sound in air is

320m{s}^{- 1},

the smallest value of the percentage change required in the length of the pipe is ________.

Correct answer

Step-by-step solution

$f = \dfrac{v}{4{L}_{1}}$

$f\left(\dfrac{320 + 0}{320 - 2}\right) = \dfrac{v}{4{L}_{2}}$

$⇒ \dfrac{{L}_{2}}{{L}_{1}} = \dfrac{318}{320}$

$⇒ \dfrac{{L}_{1} - {L}_{2}}{{L}_{1}} = 1 - \dfrac{318}{320} = \dfrac{2}{320}$

$\dfrac{\DeltaL}{L} \times 100 % = \dfrac{20}{32} % = 0 . 62 %$

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