Questions about the Public Foundation Examination for the Registration of Chemical Engineers – Physics
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The train is moving in a straight line at a speed of 25 m/s. The frequency of its whistle is 500 Hz, and the speed of sound in air is 340 m/s. A person is standing by the tracks; when the train passes by him, the frequency of the whistle as heard by him changes. The possible values are A540, B466, C432, D74. Why is the correct answer D and not A?
The frequency when the train is coming towards the person is (340+25)/340*500 Hz, while the frequency when the train is moving away is (340-25)/340*500 Hz. The change in frequency over this period is 74 Hz, which is calculated as ① minus ②
Reply to 2# lovemay39: Got it! Thank you