WEBVTT

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This is College Physics Answers
 with Shaun Dychko.

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This question is asking us for
the root mean squared

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velocity of a helium atom at a
 temperature of five Kelvin.

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So <i>V</i> RMS we're told is the square
 root of three times Boltzmann's constant

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times the absolute temperature
 divided by the mass.

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And the mass of a helium atom
 if you put in to Google,

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it will give you 4.0026 atomic mass units
 and then you have to look up

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the conversion between atomic
mass units to kilograms

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which is 1.66 times 10 to the minus 27
kilograms per atomic mass unit.

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We end up with 6.644 times 10 to
 the negative 27 kilograms

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per atom of helium.

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So the <i>V</i> RMS the  is the square
 root of three times 1.38 times

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10 to the minus 23 joules per Kelvin,
 that's Boltzmann's constant,

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times the temperature of five Kelvin divided
 by this mass of a single atom

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and that is 177 meters per second.