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A wire of length L and mass per unit length 6.0\times 10^{-3}kgm^{-1} is put under tension of 540 N. Two consecutive frequencies at which it resonates are : 420 Hz and 490 Hz . Then L in meters is :
Option: 1 2.1
Option: 2 8.1
Option: 3 1.1
Option: 4 5.1
 

Answers (1)

best_answer

 

 

Fundamental frequency   = 490 – 420 = 70 Hz

70=\frac{1}{2l}\sqrt{\frac{T}{\mu }}

\Rightarrow 70=\frac{1}{2l}\sqrt{\frac{540}{6\times 10^{-3} }}

\Rightarrow l=\frac{1}{2\times 70}\sqrt{90\times 10^{3}}=\frac{300}{140}

\Rightarrow l\approx 2.14m

Hence the correct option is (1).

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avinash.dongre

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