Physics - Elasticity Question with Solution | TestHub

The wire is rigidly held, so cooling by $12^{\circ }\mathrm{C}$ produces a thermal stress.

$\sigma =Y\alpha (20-8)=2.0\times 10^{11}\times 1.5\times 10^{-5}\times 12=3.6\times 10^7\mathrm{Pa}$

$v=\sqrt{\frac{\sigma }{\rho }}$

$v=\sqrt{\frac{3.6\times 10^7}{9.0\times 10^3}}=\sqrt{4000}\approx 63.2m/s$

This matches option D.