Question

Nahi screams at a wall and hears an echo 3s later. If the speed of sound is 332ms−1 how far is the wall from Nahi?

a. 567m
b. 488m
c. 498m
d. 553m

Answer 1

So, the distance of the wall from Nahi is (C). 498 m.

Introduction

Hi ! I'm here to help you solve this problem. This matter states that Nahi shouted and from her scream echoed, so that he could hear his own screams at intervals of time. Echoes are caused by the reflection of sound on objects that are too hard, so the sound will experience twice movement (from sound to the reflected plane and from the reflected plane in all directions, including the sound source). Based on the image I gave, the relationship between the distance of the sound source to the reflected sound field can be expressed in the following equation:

`\boxed{\sf{\bold{s = (v * t)/(2)}}}`

With the following condition :

• s = distance of sound reflector from source (m)
• v = velocity of sound through a type of medium (m/s)
• t = interval of the time until we hear the echo (s)

Problem Solving

We know that :

• v = velocity of sound through air = 332 m/s
• t = interval of the time until we hear the echo = 3s

What was asked :

• s = distance of sound reflector from source = ... m

Step by step :

`\sf{s = (v * t)/(2)}`

`\sf{s = \frac{\cancel{332} \:_(166) * 3}{\cancel{2} \:_1}}`

`\boxed{\sf{s = 498 \: m}}`

Conclusion

So, the distance of the wall from Nahi is (C). 498 m