Question

An echo is heard in 3 s. What is the distance of the reflecting surface from the source given that the sound of speed is 342 ms-1

Answer 1

d is distance of reflecting surface and t is time interval

2d = vt

$\tt d = \dfrac{vt}{2}$

Here we have

v = 342 ms^-1

time = 3sec

$\tt d = \dfrac{342\times 3}{2}$

= 513 m

Answer 2

→Speed of sound (v) = 342 ms-1

→Echo returns in time (t) = 3 s

→Distance travelled by sound = v × t = 342 × 3 = 1026 m

•In the given interval of time, sound must travel a distance which is twice the distance of reflecting surface and source.

Therefore, the distance of reflecting surface from the source = 1026/2 = 513 m.