MP Board · Class 9 · Science · SoundA person standing at a distance in front of a high vertical wall claps his hands and hears an echo after $4\text{ seconds}$. Calculate the distance of the wall from the person. (Take the speed of sound in air as $344\text{ m/s}$).

Given:

• Total time taken for the echo to be heard ($t$) = $4\text{ s}$
• Speed of sound in air ($v$) = $344\text{ m/s}$

Formula:\nLet the distance between the person and the wall be $d$.\nThe sound travels to the wall and bounces back, so total distance traveled by sound = $2d$. $$\text{Speed } (v) = \frac{\text{Total distance}}{\text{Time}} = \frac{2d}{t}$$

Step-by-step Calculation: $$2d = v \times t$$ $$2d = 344\text{ m/s} \times 4\text{ s}$$ $$2d = 1376\text{ m}$$ $$d = \frac{1376}{2} = 688\text{ m}$$

Answer:\nThe distance of the wall from the person is $688\text{ m}$.