Thermodynamics, Statistical Physics, and Quantum Mechanics

(^104) SOLUTIONS
where is thearea of the hole. Atequilibrium, so we
have
The mean free path is relatedto the volumeconcentration ofthe molecules
where is the effectivecrosssection of the molecule, which depends only
on the type of molecule, helium inbothhalves.Substituting (S.4.17.3)into
or
c)When we have tosatisfy the condition
or
whichgives for theratio of themean free paths:
4.18 Ballast Volume Pressure (Moscow Phys-Tech)
The number ofmolecules per second entering the volumeBfrom the left
container I isproportional to thedensity of the molecules in I, the
average velocity, and the area of theopening, A.The constant of
proportionality(seeProblem 4.14) isunimportant for thisproblem. So,
equating the rate of molecular flow in and out of volume B, we can write
for flow rates inequilibrium(seeFigureS.4.18)
or
(S.4.17.2) gives
by the formula