Two engines pass each other in opposite directions . One of them blows a whistle of frequency 540 Hz . Find the freqauencies heard by a passenger sitting on the other engine before and after passing each other . Velocity of both engines = 72 kmh^(-1), velocity of sound = 340 m.s^(-1) .

Two engines pass each other in opposite directions . One of them blows

1.	Two engines pass each other in opposite directions . One of them blows a whistle of frequency 540 Hz . Find the freqauencies heard by a passenger sitting on the other engine before and after passing each other . Velocity of both engines = 72 kmh^(-1), velocity of sound = 340 m.s^(-1) .
Answer» Solution :Velocity of the engine , ` u = 72 km h^(-1) = (72 xx100)/(60xx60 ) m. S^(-1) = 20M s^(-1)` Velocity of SOUND , V = 340 m ` S^(-1)` , Actual frequency , n = 540 Hz . At the TIME of approching each other , velocity of the WHISTLE ` u_(s) = + 20 m S^(-1)` Velocity of the passenger on the other engine ` u_(0) = + 20 m S^(-1)` ` therefore ` Apparent frequency , ` n. (V + u_(0))/(V + u_(s)) xx n ` ` = (340 + 20 )/(340 - 20) xx 540 = (360)/(320 ) xx 540 = 607 .5 Hz ` Again at the time of receding from each other , ` u_(s) = - 20 m S^(-1)" and " u_(o) = - 20S^(-1)` ` therefore ` Apperent frequency , ` n . = (V + u_(0))/(V- u_(s)) xx n ` ` = (340-20)/(340 - (-20)) xx 540 = (320)/(360 ) xx 540 = 480 Hz ` .