Question

A person is in front of a fort wall. The person can hear an echo of sound produced by him when minimum distance between person and wall is 16.75 m. The velocity of sound in air is:

• A. 330 m/s
• B. 335 m/s
• C. 337.5 m/s
• D. 345 m/s

Answer 1

The correct option is B 335 m/s

Minimum time for echo is $0.15$
So, distance travelled for echo is $=2\times 16.75=$ speed of sound $\times$ minimum time for echo
$\Rightarrow 2\times 16.75={\vartheta }_s\times 0.1$

$\Rightarrow {\vartheta }_s=\frac{2\times 16.75}{0.1}$$=335m/s$