A man stands 80 m in front of a cliff face. He makes a loud bang and listens for the echo. He makes a loud bang once every second. He hears an echo exactly halfway between the bang that caused it and the next bang. What is the speed of sound?
A 40m/s B 80m/s C 160m/s D 320m/s
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If the man plays a sound, then the sound waves travel towards the cliff, get reflected, return and then fall on his ear. This is how he hears an echo.
Thus the sound travels twice the distance between him and the cliff.
∴distance(s)=
2
speed×time
∴s=
2
330×2
=330 metres
Thus 330 metres is the distance between him and the 1st cliff.
Since he hears the 2nd echo after the same time interval, the 2nd cliff is also at a distance of 330 metres from him.
Hence the distance between the 2 cliffs will be 330+330=660m.
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