A man standing 825 metres away from a cliff (steep rock) fires a gun. After how long will he hear its echo ? Speed of sound in air is 330 m/s.
We have to calculate time taken by the sound wave to reach the reflecting surface.
Given: Distance between the observer and reflecting surface d = 825 m
Velocity of sound ν = 330 m/s
We know the time taken by sound wave to reach the reflecting surface is,
t = 2d/ν
⇒ t = (2)(825)/330
⇒ t = 5 s
This is the required time.
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