Question

Suppose you are 3.35 km away from a rifle range where someone is practicing shooting. If air is flowing in the direction from the shooting range to you with a speed of $5m{s}^{–1}$, then how long would it take you to hear the sound of the shot fired by him? Given that speed of sound in still air is $330m{s}^{–1.}$

• A. 10.3 s
• B. 10 s
• C. 9.3 s
• D. 10.18 s

Answer 1

The correct option is B 10 s

Speed of air, $v_a=5m{s}^{–1}$

Speed of sound in still air,$v_s=330m{s}^{–1}$

Distance, $s=3.35km=3350m$

Speed of sound when air is flowing, $v\text{'}=v_s+v_a=(330+5)m{s}^{–1}=335m{s}^{–1}$

Time to hear the sound of shot fired by him, $t=\frac{Distance}{Speed}=\frac{s}{v^{\prime }}=\frac{3350}{335}\Rightarrow t=10s$

Hence, the correct answer is option (b).