Question:
A train standing at the outer signal of a railway station blows a whistle of frequency 400 Hz still air. The train beings to move with a speed of 10 m/s towards the platform. What is the frequency of the sound for an observer standing on the platform?
Solution:
v0 = 400 Hz
vz = 10 m/s
Velocity of sound in air, va = 330 m/s
v’ is the frequency heard by the observer standing on the platform
v’ = (330)(400)/320 = 412.5 Hz
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