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Is it a myth that yelling to a coffee mug will heat it? I have been hearing my friend saying that screaming will heat coffee or water.

Řídící
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Sid
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2 Answers2

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Sound is acoustic energy. Energy is energy. If you yell at your coffee cup, some of the sound energy emitted by you toward the cup will be reflected off, but some will be absorbed into the cup, scattering and becoming generally disorganized into what is known as brownian motion... or in other words, heat. But the amount of energy involved is extremely small. You'd probably put more heat into the cup just by stirring it vigorously.

Anthony X
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This probably comes from an advertisement campaign by Physics Central. Their poster is

enter image description here

It is a silly question; no amount of yelling will appreciably heat a coffee cup. We are very inefficient at turning energy into sound. The page from which I got the photo says that a loud shot puts 0.001 W of power into the air. This is a trivial amount compared either to the rate that a cup of coffee at 50C cools purely by radiation (around 1 Watt, and this is not the main way coffee cools; it mainly cools via evaporation), or to a human metabolism (around 100 Watts).

Mark Eichenlaub
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