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) ?

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Physics

Snyder

25 December, 21:34

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) ?

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Peppy · Answer 1

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