Two strings $A$ and $B$ have lengths $l_A$ and $l_B$ and carry masses $M_A$ and $M_B$ at their lower ends,…

Two strings $A$ and $B$ have lengths $l_A$ and $l_B$ and carry masses $M_A$ and $M_B$ at their lower ends, the upper ends being supported by rigid supports. If $n_A$ and $n_B$ are their fundamental frequencies of their vibrations, the ratio of $n_A$ and $n_B$ is
  1. $\frac{M_A l_A}{M_B l_B}$
  2. $\frac{l_A}{l_B} \sqrt{\frac{M_A}{M_B}}$
  3. $\frac{M_A}{M_B} \sqrt{\frac{l_A}{l_B}}$
  4. None of these

Solution

Frequency, $n \propto \frac{\sqrt{T}}{l}$ or $n \propto \frac{\sqrt{M}}{l}$ $\therefore \frac{n_A}{n_B} = \frac{l_B}{l_A} \sqrt{\frac{M_A}{M_B}}$

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