A C-130 Hercules is traveling toward a cliff

Mission highlight

A C-130 Hercules is traveling toward a cliff at the speed of 150 m/s. Its engines emit a tone at frequency f0. We consider that the speed of sound is 340 m/s. What frequency is received by a pilot after reflection from the cliff?

Image Source: U.S. Air Force
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A person hears the whistle of an approaching train


A person standing near a railway track hears the whistle of an approaching train as having a frequency of 1600 Hz. The train’s velocity is 40 m/s.
What is the true frequency of the sound emitted by the whistle?

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Is it possible to have lightning without thunder?


Often we see a flash of lightning, but do not hear the thunder. As a rule, thunder has a short range of detection — usually less than 25 km (15 miles). Why?

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What are resonant modes?

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Why does inhaling helium make one’s voice sound funny?

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Does sound propagate further in cold weather, and if so, why?

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The silence after snowfall.


Why is it so quiet on the street after a snowfall?

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