What keeps electrons spinning around their nucleus?
in [Relativity]
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From: TomGee on 29 Mar 2005 11:52 bz, You seem to think that acceleration means "to speed up", which it does, but not in physics. TomGee
From: PD on 29 Mar 2005 12:02 mmeron(a)cars3.uchicago.edu wrote: > In article <1112038415.659261.203550(a)l41g2000cwc.googlegroups.com>, "PD" <pdraper(a)yahoo.com> writes: > > > >TomGee wrote: > >> Wormy, Bilge, PD, and all you other lemmings, > >> > >> you cannot understand that it is the _measurement_ of the force which > >> is fictional and not the feeling of being pulled out as a carousel > >> spins. You cannot make the force disappear just by invalidating your > >> own measurements. You should not think that websites are the > >ultimate > >> authority on anything, either, as subjective opinion runs rampart all > >> through it. You will learn that, Bilgy, when if ever you get to the > >> fifth grade. > >> > >> TomGee > > > >One more little experiment, Tom, on your carousel. Take your > >pocketwatch on the carousel with you and hang it by its chain between > >your thumb and forefinger. If you don't have a pocketwatch, take your > >wristwatch and hang it by a string in the same way. Now have someone > >spin you up on the carousel. > > > >You see the watch swings outward on the chain. Why, you ask? Is it > >centrifugal force? No, your fourth grade teacher says, look again. > > Yes, that's probably what the teacher will say. physics teachers know > little physics. Gee, and I thought most university-based physicists were physics teachers. > > There is ***nothing*** wrong with centrifugal force. The term > "fictitious" is misleading. True, it doesn't stem from interaction, > just from chice of reference frame. So? It is quite often convenient > to deal with a problem in an accelerated frame, rather than transform > to an inertial frame and back. And when you want to deal with a > problem in the accelerated frame and still use Newton's laws, you > include inertial forces (i much prefer the term "inertial" than the > misleading "fictitious"). > > Try the following problem. Assume that you've, say, the space shuttle > in a circular orbit around Earth, with a small mass placed in the > middle of the cargo hold, motionless relative to the shuttle. Now > give it a slight nudge. Write the Lagrangian for the system, in the > shuttle coordinates and observe the equations of motion. You'll find > a centrifugal term (and a Coriolis term, as well). Of course, if > you'll use an inertial frame, insted, these terms will disappear. But > you'll find the inertial frame far less convenient. It is a matter of > pragmatism, not ideological soap boxes. Maybe it's just me, but computational pragmatism should follow physical intuition IMHO. You are absolutely right that it's more convenient to work sometimes in the accelerated frame and see things like effective potential and a Coriolis term, and in such cases it's always a good idea to mentally note "And that thing there is because we are working in an accelerated frame." > > Consider the equation > > ax^2 + bx + c = 0 > > I'm sure that you're aware that one can always eliminate the middl > (linear) term by a proper shift of the origin of x. So? Do we call > this middle term "fictitious" and warn students never to use it? That > would be nonsense. No, but by the same token, I wouldn't say, "This problem is much more conveniently solved if we shift the origin." Indeed, I would probably work it both ways (or have students do it) so that they could see both the more intuitive but harder-to-solve method, as well as the clever trick, so that they could look at what's going on in the clever trick. > > Mind you, this has nothing to do with the value of TomGee's gibberish. > But then, since you chose to waste your time by responding to him ... Ah, we each have our chosen crosses, don't we? > > Mati Meron | "When you argue with a fool, > meron(a)cars.uchicago.edu | chances are he is doing just the same"
From: bz on 29 Mar 2005 12:11 "TomGee" <lvlus(a)hotmail.com> wrote in news:1112115150.600993.187790 @g14g2000cwa.googlegroups.com: > bz, > You seem to think that acceleration means "to speed up", which it does, > but not in physics. > TomGee I understand. It was the person I was conversing with that said that since the gyro precession was at a constant speed, there was no acceleration, thus no force and no work. Argh. I have been trying to administer clue. I have learned a few things myself during research to refute his ideas. -- bz please pardon my infinite ignorance, the set-of-things-I-do-not-know is an infinite set. bz+sp(a)ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap
From: PD on 29 Mar 2005 12:53 Gregory L. Hansen wrote: > In article <slrnd4h9dg.6h5.dubious(a)radioactivex.lebesque-al.net>, > Bilge <cranks(a)fghfgigtu.com> wrote: > > mmeron(a)cars3.uchicago.edu: > > > > >I don't see anything in the formulation of newton's laws saying that > > >forces must be traceable to fundamental interactions. What should be > > >taught is that there are "physical forces" which are, indeed, a > > >measure of interactions between objects, and there may be additional > > >"inertial forces" which are an artifact of the choice of reference > > >frame. But being an artifact, does not mean that they've no > > > > ``Inertial force'' is an oxymoron. If ``inertial forces'' are > >to be considered forces, then the word ``force'' is nothing but > >a placeholder for a noun, since anything is then a force. > > A force makes something accelerate. If you're at rest in an accelerate > frame you might see a ball accelerate spontaneously. If it accelerated, a > force must have acted on it. "Inertial force" might not be the best name > for that because they don't appear in an inertial reference frame. > -- It's a common, common misconception that the motion produces the force. Battling this is a key beachhead. PD
From: RP on 29 Mar 2005 13:02
mmeron(a)cars3.uchicago.edu wrote: > In article <d2ac7c$65m$5(a)rainier.uits.indiana.edu>, glhansen(a)steel.ucs.indiana.edu (Gregory L. Hansen) writes: > >>In article <slrnd4h9dg.6h5.dubious(a)radioactivex.lebesque-al.net>, >>Bilge <cranks(a)fghfgigtu.com> wrote: >> >>>mmeron(a)cars3.uchicago.edu: >>> >>> >>>>I don't see anything in the formulation of newton's laws saying that >>>>forces must be traceable to fundamental interactions. What should be >>>>taught is that there are "physical forces" which are, indeed, a >>>>measure of interactions between objects, and there may be additional >>>>"inertial forces" which are an artifact of the choice of reference >>>>frame. But being an artifact, does not mean that they've no >>> >>> ``Inertial force'' is an oxymoron. If ``inertial forces'' are >>>to be considered forces, then the word ``force'' is nothing but >>>a placeholder for a noun, since anything is then a force. >> >>A force makes something accelerate. If you're at rest in an accelerate >>frame you might see a ball accelerate spontaneously. If it accelerated, a >>force must have acted on it. "Inertial force" might not be the best name >>for that because they don't appear in an inertial reference frame. >>-- > > Got a point. Lets call them "non-inertial forces". How about artificial gravitational forces. Richard Perry |