A road runs midway between two parallel rows of buildings. A motorist moving with a speed of 36 km/hr sounds the horn. He hears the echo one second after he has sounded the horn. Then the distance between the two rows of buildings, will be (Velocity of sound is 330 m/s)

Explanation

The situation is shown in figure-6.8.

Given the velocity ofmotorist = 36 km/hour = 10m/s. So he travels a distance of 10 m in one second. He will hear the firstechoafterthe soundhad travelled330 m through the least path i.e., reflected at point B.
From figure-6.8, we have
`AB = sqrt((AF^(2) + AF^(2)) ) = sqrt((5^(2) + x^(2)))`
And `AB + BC = 2sqrt((5^(2) + x^(2)))`
But we also have AB + BC= 330 m
Thus `2sqrt((5^(2) + x^(2)))` = 300 m
solving we get x = 164.9 m
othedistance between the two rows of building g =2 x=329.8 m. He will hear the second echo at E after the sound had travelled a further "distance of330 m, reflecting from the other row i.e., 2 seconds after the horn is sounded.