411 REFERENCE · Wikibooks
Statistical Mechanics/Ideal Gas
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Consider an ensemble of molecules.
Take a particular molecule, while the others form a heat reservoir at temperature T.
The energy(E)is kinetic = p2/2m = 1/2mv2,
P(E) α e-βE α e-β(p2/2m)
The probability that the molecule lies between r→ and r→+