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]
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
It separates things by density, not mass. On Tue, Apr 29, 2008 at 6:50 PM, Dan Asimov <dasimov@earthlink.net> wrote:
Mike Speciner wrote:
<< [quote of passage from NY Times article that Mike evidently considers erroneous]
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
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Pace Eugene, it doesn't seem to me that this question has yet received a satisfactory answer. Why do objects fall at all, under the influence either of gravity or a centrifuge? Mechanics isn't my strong point --- but I think the implicit subtext is that [ignoring inertia for the moment] the system attempts to minimise its potential energy, which involves high density regions migrating in the direction of the force field. WFL On 4/30/08, Mike Stay <metaweta@gmail.com> wrote:
It separates things by density, not mass.
On Tue, Apr 29, 2008 at 6:50 PM, Dan Asimov <dasimov@earthlink.net> wrote:
Mike Speciner wrote:
<< [quote of passage from NY Times article that Mike evidently considers erroneous]
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
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-- Mike Stay - metaweta@gmail.com http://math.ucr.edu/~mike http://reperiendi.wordpress.com
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Isotopes have essentially the same chemical properties, including the "size" of the molecules. The difference is in the number of neutrons, so one isotope would then have a higher (or lower) density than another. Since systems tend towards the lowest energy state consistent with any constraints (as noted below), the higher density material tends towards the "bottom" of the tube in the centrifuge. Gravitational force is proportional to the mass of an object, although the acceleration is not. Since pressure is the force per unit area, you could (this is not rigorous) think of a heavier isotope molecule that is on top of lighter isotope molecules as having a greater force down than the buoyant force upwards from the lighter molecules pushing back on the heavier one (this is because, chemically, they have the same "area", but different masses or forces). Thus, it would tend to fall downward, through the lighter isotope molecules. Objects accelerate (fall) if there is a net force on them--one of Newton's Laws. Bill C. -----Original Message----- From: math-fun-bounces@mailman.xmission.com [mailto:math-fun-bounces@mailman.xmission.com] On Behalf Of Fred lunnon Sent: Tuesday, April 29, 2008 10:18 PM To: math-fun Subject: Re: [math-fun] And I suppose heavy objects fall faster than light ones? Pace Eugene, it doesn't seem to me that this question has yet received a satisfactory answer. Why do objects fall at all, under the influence either of gravity or a centrifuge? Mechanics isn't my strong point --- but I think the implicit subtext is that [ignoring inertia for the moment] the system attempts to minimise its potential energy, which involves high density regions migrating in the direction of the force field. WFL On 4/30/08, Mike Stay <metaweta@gmail.com> wrote:
It separates things by density, not mass.
On Tue, Apr 29, 2008 at 6:50 PM, Dan Asimov <dasimov@earthlink.net> wrote:
Mike Speciner wrote:
<< [quote of passage from NY Times article that Mike evidently considers erroneous] > >> > > 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 > > > >
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-- Mike Stay - metaweta@gmail.com http://math.ucr.edu/~mike http://reperiendi.wordpress.com
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participants (4)
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Cordwell, William R -
Dan Asimov -
Fred lunnon -
Mike Stay