The frequency of a steam train whistle as it approaches you is 552 hz. after it passes you, its frequency is measured as 486 hz. how fast was the train moving (assume constant velocity)?

Approaching frequency= 552 Hz  

Passing frequency = 486 Hz  

The actual whistle frequency is (552 + 486)/2 Hz = 519 Hz  

Assume the speed of sound = 340 m/s  

Using the Doppler formula: (519/486) -1 = 0.0679

The train speed  = 0.0679 * 340 m/s = 23.09  m/s

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