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a man fires a bullet towards …

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a man fires a bullet towards cliff and hears echo after 4 sec he moves towards the clife nabout 150m and agains fire now he hears echo after3.6s what is the distance from his first position[ASSUME VELOCITY OF SOUND IS NOT KNOWN TO YOU]

  • 1 answers

Naveen Sharma 7 years, 2 months ago

Ans. Let the Distance  b/w cliff and man = d m

Then total distance cover by sound = 2d m

Velocity of Sound = v 

Then 

\(v = {2d \over 4} = {d\over 2}\space\space\space\space\space\space\space\space\space\space ......[1]\)

As He move 150m  towards The cliff, 

Now distance b/w man and cliff = d-150 m

Total distance covered by Sound = 2(d-150) m

So 

\(v = {2(d-150)\over 3.6} = {2(d-150)\times 10\over 36} = {5(d-150)\over 9} \space \space \space \space \space ......[2]\)

As velocity of sound is same, then 

from (1) and (2)

=> \({d\over 2}= {5(d-150)\over 9} \)

=> \(9d = 10d - 1500 \)

=> \(10d- 9d = 1500 => d = 1500 \)

Distance b/w man and cliff = 1500 m

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