If the centrifuge spins at angular velocity omega, the potential energy of a molecule of mass m in the centrifugal potential is V(r) = - (1/2) m omega^2 r^2. In a gas at temperature T, the equilibrium density varies as exp(- V/(r)/kT), k being Boltzmann's constant. The two molecules U235F6 and U238F6 distribute independently, and since they have slightly different mass, the gas near the axis is slightly enriched, and the gas near the periphery is slightly depleted, in U235. Since the peripheral velocity is v = omega R, R the radius of the object, the separatory power is proportional to the square of the peripheral velocity of the rotor, and independent of its radius. Original Message ---- From: Dan Asimov <dasimov@earthlink.net> To: math-fun <math-fun@mailman.xmission.com> Sent: Tuesday, April 29, 2008 6:50:56 PM Subject: Re: [math-fun] And I suppose heavy objects fall faster than light ones? Mike Speciner wrote: << [quote of passage from NY Times article that Mike evidently considers erroneous]

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Mike, I don't recall if I ever understood just how centrifuges work. Would you be so kind as to explain? --Dan _____________________________________________________________________ "It don't mean a thing if it ain't got that certain je ne sais quoi." --Peter Schickele _______________________________________________ math-fun mailing list math-fun@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun ____________________________________________________________________________________ Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ