Question

If the Young's modulus of the material of a rod is $2 \times 10^{11} \,N\, m ^{-2}$ and its density is $8000 \,kg\, m ^{-3}$, the time taken by a sound wave to traverse $1\, m$ of the rod will be

• A. $3 \times 10^{-4} s$
• B. $2 \times 10^{-4} s$
• C. $3 \times 10^{-2} s$
• D. $2 \times 10^{-2} s$

Answer 1

Answer: (B)

The speed of sound waves in the rod is
$v=\sqrt{\frac{Y}{\rho}}=\sqrt{\frac{2 \times 10^{11}}{8000}}=5000\, m\, s ^{-1}$
$\therefore $Time taken $=\frac{1}{5000}=2 \times 10^{-4} \,s$