Two boys A and B are standing 1.02 km apart from each other. They Stand at the same distance from a vertical hillock .A fires a shot and B hear echo 2 seconds after hearing the direct sound. find the distance of A from the hillock. Speed of sound in air =340 metre per second.

Total distance covered by the sound and its reflection = 2d
where d is the distance between vertical hillock and one of the man.

Time taken for the echo to be heard = 2 s

Let the speed of sound in air be 340 m/s.

We know , Speed = Distance /time 
                      340 = 2d/ 2
                       d   = 340 m





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