A car is parked 17.0 m directly south of a railroad crossing. A train is approac

Question

A car is parked 17.0 m directly south of a railroad crossing. A train is approaching the crossing from the west, heading directly east at a speed of 60.0 m/s. The train sounds a short blast of its 340-Hz horn when it reaches a point 18.0 m west of the crossing. What frequency does the car's driver hear when the horn blast reaches the car? The speed of sound in air is 343 m/s. (Hint: Assume that only the component of the train's velocity that is directed towards the car affects the frequency heard by the driver.)

Explanation / Answer

@ = tan^-1(17 / 18) = 43.36 deg

using doppler effect;

f = (v + vr)f0 / (v + vs)

v = 343 m/s

vr = velocity of reciver = 0

vs = velocity of source = - 60cos43.46=- 43.62 m/s

f = (343 - 0 ) (340) / (343- 43.62) =389.5 hz

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