A child hear an echo from a cliff 10 seconds after the sound from a powerful cracker is produced .  how far away is the cliff from the child ? (velocity of sound in air as 350 m/s).

Velocity of sound, v = 350 m/s 

Time taken by the sound to return from the cliff, t = 10 s

Let, x be the distance between the cliff and the boy.

= 3500m

=> x = 1750 m

  • 6

 As the echo is returning it covers twice the distance.

So

2*distance = Velocity*Time

2d = 3500

d = 3500/2 = 1750m

Thumbs up please

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