Question

An echo returned in 3 s. what is the distance of the reflecting surface from the source, given the speed of sound ???? is 342m/s.

Answer 1

Let the required distance be d m.
Sound travels 2d m in 3 s.
Speed of sound(v) = 342 m/s.
By the problem, 
=>   2d/3=342
=>   d = 513 m
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Answer 2

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Speed of sound, v = 342 m s−1

Echo returns in time, t = 3 s

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

In the given time interval, sound has to travel a distance that is twice the distance of the reflecting surface and the source.

Hence, the distance of the reflecting surface from the source = (1026/2)m= 513m

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