\(\frac{1}{2}m{v^2} = \frac{1}{2}\frac{{YA{l^2}}}{L}\) \(\Rightarrow \) \(v = \sqrt {\frac{{YA{l^2}}}{{mL}}} \)
\( = \sqrt {\frac{{5 \times {{10}^8} \times 25 \times {{10}^{ - 6}} \times {{(5 \times {{10}^{ - 2}})}^2}}}{{5 \times {{10}^{ - 3}} \times 10 \times {{10}^{ - 2}}}}} = 250\;m/s\)