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Two wires of radii in the ratio 2 : 3,lengths in the ratio 3 : 5.Forces applied in the ratio 5 : 7 with young modulii in the ratio 3 : 4.The change in length is in the ratio

$\begin{array}{1 1}(A)\;\large\frac{7}{9}\\(B)\;\large\frac{25}{7}\\(C)\;\large\frac{9}{7}\\(D)\;\text{None}\end{array} $

1 Answer

$\large\frac{\Delta l_1}{\Delta l_2}=(\frac{f_1}{f_2})(\frac{l_1}{l_2})(\frac{a_2}{a_1})(\frac{Y_2}{Y_1})$
$\Rightarrow \large\frac{5}{7}\times \frac{3}{5}\times \frac{9}{4}\times \frac{4}{3}$
$\Rightarrow \large\frac{9}{7}$
Hence (C) is the correct answer.
answered May 9, 2014 by sreemathi.v

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