Question

A person claps his hands in an empty room. He hears the echo of the sound after 5 seconds. What is the distance between the person and the wall of the room?
(Take the speed of sound in air = 340 m <!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> $s^{-1}$)

• A.
  912 m
• B.
  3500 m
• C.
  850 m
• D.
  999 m

Answer 1

The correct option is C

850 m
Let the distance between the source of sound and the wall be ‘d’.
Hence, the total distance travelled by the sound (d’) = 2d

Given,
Time taken for the echo to reach the source (t) = 5 s
Speed of the sound wave (v)
= 340 m$s^{-1}$

From the formula of speed,
Speed = $\frac{Distance}{Time}$
v = $\frac{d^{\prime }}{t}$
v = $\frac{2d}{t}$
d = $\frac{(v\times t)}{2}$
d = $\frac{(340\times 5)}{2}$
d = 850 m
Thus, the distance between the person and the wall is 850 m.