What keeps electrons spinning around their nucleus?
in [Relativity]
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From: Creighton Hogg on 31 Mar 2005 08:09 On Thu, 31 Mar 2005 mmeron(a)cars3.uchicago.edu wrote: > In article <Pine.LNX.4.44.0503301941040.20954-100000(a)dill.hep.wisc.edu>, Creighton Hogg <wchogg(a)hep.wisc.edu> writes: > >Indeed this is the case as I've seen it as well. I learned > >it on my own in 10th grade because I was bored and > >frustrated. There's no reason why kids that age can't > >handle it. > > > Try to explain this to the school boards (and be prepared to face > charges of elitism). I don't really understand why people fight so hard against teaching math and science earlier or why they fight so hard against making students learn it at all. It's like some kindof cultural block against it. I sometimes think there's become some kindof two-tone deafness about children and children's education. Sometimes it seems like people think you can be loving, caring, and accepting of whatever a child does, or you can be a sadistic monster that tormets children day and night with nothing in between, and since telling a child that they did something wrong isn't being accepting...
From: Tom Capizzi on 31 Mar 2005 08:40 "TomGee" <lvlus(a)hotmail.com> wrote in message news:1112244079.328719.15960(a)f14g2000cwb.googlegroups.com... > > Tom Capizzi wrote: >> "TomGee" <lvlus(a)hotmail.com> wrote in message >> news:1112061355.884198.62110(a)g14g2000cwa.googlegroups.com... >> > >> > PD wrote: >> > SNIP >> >> >> Centrifugal forces don't exist. They are mistakes of perception and > no force >> actually pushes out. >> >> > Not so. The inertial force of a mass wants it to go straight but the > gravitational force wants it to turn and if an orbit results the net > force is on the side of gravity but just enough to pull it into orbit. Inertial force only exists in the rotating frame. Inertia causing a body to move in a straight line is a property of a non-rotating frame, as such straight lines appear to be curves in a rotating frame. You're mixing frames of reference. >> >> >> >> >> >> If this comes as a shock to you, perhaps it's because >> >> you're relying on the physics you learned in the 3rd grade. >> >> 3. In circular motion, you'll note that the velocity is tangent to >> > the >> >> circular trajectory, perpendicular to the radius of the circle. > Both >> >> the true, centripetal force and the false, centrifugal "force" are >> >> along the radius of the circle, perpendicular to the velocity. >> >> >> >> >> > Velocity is a vector but you are using it to mean "direction". > Speed >> > cannot be tangent nor perpendicular to anything, so you're babbling >> > now. >> >> Talking about yourself again? Vector: >> 2. (Math.) A directed quantity, as a straight line, a force, or a > velocity. >> Vectors are said to be equal when their directions are the same their > >> magnitudes equal. Cf. Scalar. [1913 Webster] >> >> > That's what I said, velocity is a vector. It is also "speed", but that > is not what he means. If he is saying that the forces are imposed He is saying exactly what he means: the radius of the circle is at right angles to the velocity (vector). It is inappropriate to claim anything is perpendicular to speed. Velocity (a vector) is directed parallel to the circumference (tangent) which is perpendicular to the radius. The centripetal force is perpendicular to the velocity vector, and anti-parallel to the radius. All of this is a simple mathematical consequence of the derivative of a complex exponential which is necessary to describe circular motion. Each degree of differentiation adds a factor of i (square root of -1) to the result. If the radius is a vector of constant magnitude which changes direction at a constant rate, then the 1st derivative (velocity) is rotated 90 degrees to the radius vector, is also constant in magnitude and also changes direction at a constant rate. The 2nd derivative (acceleration) is rotated another 90 degrees, making it 180 degrees away from the direction of the radius (which is anti-parallel), also has constant magnitude and also changes direction at a constant rate. > perpendicular to the speed, if he means to use velocity for speed, that > would be nonsense, as I noted above. If he means to say that the > direction of the mass quantity is tangent to the path of the object > (trajectory), that too makes no sense. Makes sense to me. At any given point on the trajectory of any object the direction is defined to be the tangent at that point. >> >> >> >> There is >> >> no way that a force that is perpendicular to the velocity can > change >> >> the magnitude of the velocity, nor does it help in any way to >> > maintain >> >> the velocity. >> >> >> >> >> > Mygawd Im talking to a child! There is no magnitude in velocity! > It >> > is a measure of the rate of change of position of something wrt > time, >> > speed, and direction. >> >> See above definition of vector. Clearly it has magnitude. You don't > know >> what you are talking about again. >> >> > If magnitude and quantity had the same meaning, we would have use for > only one and not both. Since you want to quibble about definitions, what in Gee-speak do you claim is the difference? Besides, have you never heard of synonyms? >> >> > >> >> 4. Newton's 1st law should also have been taught to you in 3rd > grade >> >> physics, and you should be reminded that, even in the absence of >> >> forces, objects in motion tend to stay in motion. >> >> >> >> >> > I can't believe you are so ignorant as to claim that the 2nd law > allows >> > objects to remain in orbit if all forces are removed. I let that >> > foolishness go by the first time you said it, to keep from making > you >> > look sillier, but it is you who brings that onto yourself, not me, > with >> > your absurdities. >> >> Look again. It says 1st law. If you actually read the 1st law you > would know >> that it says motion "in the same direction", that is to say a > straight line, >> unless acted on by unbalanced forces. >> >> > If you actually understood what is being said you would know circular > motion is not a straight line. Or do you agree with Silly there that > objects in circular motion, orbits or orbitals, will continue in such > motion even when the forces maintaining them in such motion are > removed? You misrepresent what others say and expect agreement on your error? >> >> >> >> >> >> Now, if you find any of this to be intuitively wrong, then your >> > problem >> >> is not with special relativity, it's with 3rd grade physics. If > you >> >> would like corroboration that any of the above is true or false, > then >> >> simply itemize the thing you think is wrong and ask the newsgroup. >> >> >> >> >> > All but a few have dared to agree with me or disagree with you, > but, as >> > I said in my first post in this thread, I find it incredible that > the >> > first 8 posters could not answer a simple question properly. > Either >> > they all think you're the greatest thing since Einstein or they > will >> > agree to anything so long as they don't have to agree with me. >> > >> >> The question was what keeps the electron spinning around the nucleus, > not >> what keeps it attracted. Maybe they are the same thing to you, but > they are >> actually perpendicular directions. In physics, perpendicular > components, >> even of the same vector, are independent. If you wanted to know what >> attracts the electron, you should have asked a better question. Of > course, >> it seems you already had the answer you wanted, but were trying to > bait a >> troll's trap. >> >> > Hey, I did not ask the questions. You seem to think that the question > was what keeps it moving? It was not. He asked what keeps it moving > _around the nucleus_, as you correctly state above. You don't seem to > see the distinction between those two questions, but that is not my Your error. I explicitly pointed out that the two questions are different above. Earlier you made a spurious claim about speed when the poster specifically used the term velocity. Below you make reference to the irrelevant "free electron". Nobody is talking about free electrons but you. > fault. Something keeps free electrons moving, and as free electrons, > they are not then moving around any nucleus. Since the question was > that specific, so was my answer. > > TomGee >
From: PD on 31 Mar 2005 10:04 Creighton Hogg wrote: > On Thu, 31 Mar 2005 mmeron(a)cars3.uchicago.edu wrote: > > > In article <Pine.LNX.4.44.0503301941040.20954-100000(a)dill.hep.wisc.edu>, Creighton Hogg <wchogg(a)hep.wisc.edu> writes: > > >Indeed this is the case as I've seen it as well. I learned > > >it on my own in 10th grade because I was bored and > > >frustrated. There's no reason why kids that age can't > > >handle it. > > > > > Try to explain this to the school boards (and be prepared to face > > charges of elitism). > > I don't really understand why people fight so hard against > teaching math and science earlier or why they fight so hard > against making students learn it at all. It's like some > kindof cultural block against it. [snip] Actually, for this I blame university science departments, *particularly* physics. Physics departments generally do not even *consider* training students to be future junior high or high school physics teachers. They are so all-fired focussed on producing research physicists or engineers, and yet they complain about the miserable preparation incoming students have. I recall one time joining forces with the school of education to have a physics lab at an amusement park, which I was arranging for my "physics for the terrified" class. I had written up a lab manual, which mind you was directed at liberal arts students, and gave it to the professor in the education department. She sent it back, horrified, saying that it was above the heads of her students. Keep in mind her students were our future high school science teachers. When physics majors can graduate with a B.S. or even a B.A. and be guided to teaching physics in secondary school by their departments, then we'll have made a step forward. Heck, even a masters in physics is essentially a throwaway degree -- aim all those people at teaching physics at the secondary level. PD
From: jmfbahciv on 31 Mar 2005 09:08 In article <3avtadF6bq14rU1(a)individual.net>, "robert j. kolker" <nowhere(a)nowhere.net> wrote: > > >jmfbahciv(a)aol.com wrote: > >> >> The Mass. board of education is now trying to add science >> as part of the high school graduation requirement. The >> year proposed was 2008 but news broadcasts are now saying >> it can't happen until 2010. Listen for the whinging from >> teachers' unions. One of them is already running ads that >> they can't teach science because there is only 1 microscope/ >> 10 students. That's an awfully high ratio even though the >> ads want you to think that it's too low. When I went to >> high school, I estimate the ration to be 1/100. > >While the relative scarcity of lab equipment 1 in 10 is not a scarcity. I would call it wastage. > .might impact the quality of >lab based science instruction there is no shortage of blackboards or >overhead viewscreen devices. The theoretical aspects of physics and the >associated mathematics can be taught with the material resources >currently at hand. > >On the other hand biology and chemistry does not a substatial laboratory >practice component to be taught properly. If one does not dissect the >worm or frog one has no sense of the asymmetry of internal structure of >complicated organisms. Each student does not need biology and chemistry lab equipment 7x24. A class of 30 use the lab for 45 minutes at a time. Multiply by number of classes per day. ...although I have been noticing that the school buses are now dumping kids at 14:15 lately. That means that a kid gets 4 hours of class? /BAH Subtract a hundred and four for e-mail.
From: jmfbahciv on 31 Mar 2005 09:19
In article <xXF2e.18184$C7.13791(a)news-server.bigpond.net.au>, "Bill Hobba" <bhobba(a)rubbish.net.au> wrote: > ><jmfbahciv(a)aol.com> wrote in message news:RtidnWcXTP7uC9ffRVn-2Q(a)rcn.net... >> In article <07n2e.41$45.5359(a)news.uchicago.edu>, >> mmeron(a)cars3.uchicago.edu wrote: >> >In article <GJk2e.16991$C7.9156(a)news-server.bigpond.net.au>, "Bill Hobba" >> <bhobba(a)rubbish.net.au> writes: >> <snip> >> >> >>> That said, there is certainly room to analyze the way things are being >> >>> taught. The natural tendency is to teach things in the historic order >> >>> in which they were developed (an educational equivalent of "ontogeny >> >>> recapitulates philogeny"). That may not necessarily be the best >> >>> course of action. >> >> >> >>Having read the replies by yourself, Gregory and PD I relise in >> suggesting >> >>that I had forgetten one of the things I emphasize in education. It >must >> >>actually be tested rather than be based on what I or others may think >> >>belongs in a course. >> >> >> >Aye, exactly. >> >> The Mass. board of education is now trying to add science >> as part of the high school graduation requirement. > >Hmmmm. Although a proponent of science teaching in schools I am not sure if >knowledge of science beyond grade 10 or even grade 8 is required. Many >professions such as law, graphic design etc require only minimal science. Nope. My college physics classmates, who were art majors, used the physics they learned in their graphics business. Lawyers have to be able to learn about anything that has anything to do with their law practice; there is requirement for science knowledge in all law aspects: contracts, criminal, civil, etc. Didn't you watch the O.J. trial? A side effect of learning science is to learn how to think analytically. Our best bit gods had science and/or math degree_s_. I don't know of a single aspect of living that doesn't require analytical thinking of some flavor. Knowing what to do when the light bulb doesn't emit light requires analytical thinking. > .. I >think the interests of students would be better served by examining the >needs of each student on an individual basis and igniting an interest in >math and science (look what Jaime Escalante did) rather than setting >minimums. If you have to have a production line, then handtooling is not an option. The problem with our education system is that the end of the production line has been moved to fourth year college. Thus, any finetuning doesn't occur until grad level. The fine tuning should have happened 8 years before during high school. > >> The >> year proposed was 2008 but news broadcasts are now saying >> it can't happen until 2010. Listen for the whinging from >> teachers' unions. One of them is already running ads that >> they can't teach science because there is only 1 microscope/ >> 10 students. That's an awfully high ratio even though the >> ads want you to think that it's too low. When I went to >> high school, I estimate the ration to be 1/100. > >The carry on of unions sometimes is pathetic - and where I worked I was a >union delegate. But keep in mind their purpose is to get the best deal >possible for their members. Nope. That is not what unions do. Oh, that's how they get started but they quickly become a socialist management layer where quality of the product is a non-goal. Note that our definition of non-goal is to always tradeoff against the non-goal. > .... They couch it in the language we want what is >best for the students but it is easy to see what there true agenda is. If >they were really concerned we would see more teachers taking matters into >their own hands - teachers like Jaime Escalante. Here in Australia it is >well known that a much higher percentage of teachers send their students to >private schools. When reporters ask about this you know what the union >advises the teachers to say - we are just exercising our right to choose. >They must think people are brain dead or something. And how did these "poorly" paid teachers get all that lovely money to send their kids to private school? /BAH Subtract a hundred and four for e-mail. |