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> 以速度u="20" m/s奔驰的火车，鸣笛声频率为275 Hz，已知常温下空气的声速v="340" m/s。 (1)当火车驶来时，站在铁道旁的观察者听到的笛声频率是多少？ (2)当火车驶去时，站在铁道旁的观察者听到的笛声频率是多少？

问题：

发布时间：2024-09-07

以速度u="20" m/s奔驰的火车，鸣笛声频率为275 Hz，已知常温下空气的声速v="340" m/s。
(1)当火车驶来时，站在铁道旁的观察者听到的笛声频率是多少？
(2)当火车驶去时，站在铁道旁的观察者听到的笛声频率是多少？

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