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A boy standing in front of wall at a dis...

A boy standing in front of wall at a distance of `85 m` produces `2` claps per second. He notices that the sound of his clapping coincides with the echo. The echo is heard only once when clapping is stopped. Calcualte the speed of sound.

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Here, distance of the boy from the wall, `d = 85 m`
time taken by the echo to be heard, `t = (1)/(2) s = 0.5 s`
If `d` is distance between the boy and the wall, total distance travelled by sound in going and coming back `= 2 d`
As distance travelled by sound = speed of sound xx time,
`2 d = v t` or `v = (2 d)/(t) = (2 xx 85)/(0.5) = 340 m//s`.
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