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Everything posted by studiot
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I think there are some doubts about solid helium, but I would have to look this up. Further the question of phases becomes more complicated when talking about compounds (alloys in the case of metals) as you get all sorts of complicated phase and eutectic diagrams.
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No it's not clear. And your diagram is not a free body diagram of the wedge, despite you labelling it as such.
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So mercury is not a metal? What about the liquid stuff they make in a steelworks?
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I don't see them mentioned once. Have you not learned how to lay out your work so that others can follow what you are doing?
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You tell me that something is moving, so why are you not applying Newton's Laws of motion?
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This is taken from Solid State Chemistry by Smart and Moore. I have highlighted the relevant bits on the two pages.
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Yes I did , how is that incompatible with other things that have been said? So , I merely gave this as an example that hydrogen can be considered a metal and whne it is, its gaseous form is undoubtedly that of molecules, formed from covalently bonded atoms. I also gave experimental measurements showing that mercury vapour is a conductor. I also said that most metals only exist as vapour at higher temperatures and this brings other considerations. So how is any of that incompatible?
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well gsin(theta) is an acceleration so you can apply Newton's second law yes?
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It can't be both fixed and accelerating. Produce a decent drawing to show what you mean.
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What is all the fuss about? Two (or more) coats are used because it is pretty well impossible to achieve complete coverage without minute holes in the paint film using only (despite the adverts). So long as the second coat fills these holes it doesn't really matter if its coverage is not so good on the bits that have already been painted. For instance, surely you only do the cutting in once ?
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Then how is it accelerating?
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I don't know why I should tell you this since you have been arrogantly dismissive towards my comments and now fail completely to address them, in defiance of the rules here. But your textbook tells you only part of the story. There were originally two definitions of the real numbers, coming from as opposite approaches as possible (synthetic v analytic) due to Cantor and Dedekind. Your textbook is offering you what are known as Dedekind cuts. They were later shown to be equivalent. A good textbook will do the same. see here. https://www.google.co.uk/search?source=hp&ei=76G3W6GkB-WprgTA-aqoDg&q=equivalence+of+dedekind+and+cantors+real+numbers&oq=equivalence+of+dedekind+and+cantors+real+numbers&gs_l=psy-ab.3...1250.22502.0.22698.50.48.0.2.2.0.276.6196.0j36j2.38.0....0...1c.1.64.psy-ab..10.31.4860...0j0i131k1j0i10k1j0i22i30k1j0i22i10i30k1j33i22i29i30k1j33i160k1j33i10i160k1j33i10k1j33i21k1j33i10i21k1.0.8SA5CoIrGpU
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If there is relative motion between the block and the wedge then you must apply Newton's Laws resolved parallel and perpendicular to the interface. It is not then an equilibrium question. Is this homework?
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I think you will find that whilst you have the corner contributions correct, the question (can we see the exact wording) refers to alternate face centered cubic, which has B atoms on only two opposite faces. Therefore there are only two B atoms, not 6 or 3. Is this homework?
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The Scientific Method -- is there such a thing?
studiot replied to Reg Prescott's topic in General Philosophy
Rubbish, there are plenty of useful statements that can be made about something non existent. If it doesn't exist it has exactly zero mass (or does it, wait and see) Does a hole exist? What is the temperature of a hole? What colour is a hole? What is the value of the centrifugal force due to the Earth's rotation, in London? Use your(scientific imagination) -
Perhaps if your sketch was a bit neater it would be more obvious. I can't read the mass of the block resting on the wedge. However if the wedge is resting on the ground and the block is simply resting on the wedge then the pair of them (wedge and block) must exert a combine thrust on the ground equal to the combined mass time g ie (ma + mb)g. Unless they then start flying, Newton's third law tells us that the ground must therefore exert a reaction equal to this.
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That's exactly what I said they were. Look at the most common of the many versions of the periodic table. Where is hydrogen placed (in which column ?) or just look here https://www.google.co.uk/search?source=hp&ei=C0q3W9uCOI2_gQbuso2gCw&q=metallic+hydrogen&oq=metallic+hydrogen&gs_l=psy-ab.3..0l10.1408.4630.0.4936.17.11.0.5.5.0.276.1596.3j7j1.11.0....0...1c.1.64.psy-ab..1.16.1732...0i131k1.0.cOwCtv_yKzo
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The Scientific Method -- is there such a thing?
studiot replied to Reg Prescott's topic in General Philosophy
So you refuse to have a discussion about your stated objective. Then to hell with you. -
The Scientific Method -- is there such a thing?
studiot replied to Reg Prescott's topic in General Philosophy
Yes indeed one off events. I tried to discuss this with the OP in his previous thread, but he refused to consider it. What is the exact breaking load of a specific piece of timber? There is only one way to find out; that is to break it and measure the load. but once you have broken it you cannot do it again. If the thread and attempted discussion I am remembering was due to someone else I apologise in advance, but it was recent. -
The Scientific Method -- is there such a thing?
studiot replied to Reg Prescott's topic in General Philosophy
Is that all you have to say? I agreed with your opening proposition and offered my thoughts in relation to your later question concerning a better definition. Why not move forward? -
Thank you. There are indeed multiple issues later in the 'proof'. But at the stage I am discussing, only the reals and a single dimension have been introduced. Whatever is said about this needs to be self consistent, unambiguous and preferably in line with the simplest conventions in normal use. It is noticable that mathematicians on other full blooded mathematics forums are being confused by the definitions and notation employed in the OP's presentation.
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The Scientific Method -- is there such a thing?
studiot replied to Reg Prescott's topic in General Philosophy
I agree. But that is no reason to attack science and scientists in general. I would say that the scientific method is the rational application of scientific principles to an issue or enquiry. This definition comes with several riders or notes. 1) By definition the method is a process. It does not include the generation of the issue or enquiry in the first place. That is separate and (in my view) the source of much confusion. 2) There are multiple principles. some are more important than others. The balance between these is case specific. 3) Godel's theorems tell us that, no matter how good they are, inductive processes alone cannot answer all question that can be asked of an axiomatic system. 4) So review and verification (preferably independent) is one of the most important of the scientific principles. -
I think it is a great deal more complicated than that. Furthermore mercury vapour, for example, is conductive. http://www.jetp.ac.ru/cgi-bin/dn/e_022_01_0089.pdf This is a big question. Vapour state materials may or may not be single atoms. Many are molecules formed from covalently bonded atoms. Hydrogen is one such and under some systems of classification is a 'metal'. But there is a fourth state of matter - the plasma state. This is formed from free ions of a material. The boiling temperatures of most metals are such that gaseous particles are highly energetic so a portion of them are always likely to be ionised. So there will nealy always be a measure of conductivity.
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Thank you for responding to my question. Here is your first sentence. I asserted that this is ambiguous and you say you can't see why. So here it is in detail. Let R be separated between the real numbers in the neighborhood of the origin zerohat and....... So does this mean zerohat refers to the neighborhood or to the origin itself ? That first part of the sentence could be taken to mean either. So it is ambiguous. The difference is vital to the rest of the working. Since you very shortly write equation 1 which is invalid if zerohat refers to the neighborhood I did you the courtesy of assuming it refers to the origin itself. This then leaves the issue of why you have chosen to provide two different but similar symbols for the same thing. Surely a recipe for confusion. Thank you for your comment and also the ones about the working. It is difficult to sort out when the working refers to a set (neighborhood) and when a real number I agree with your comment about the separation of the reals into neighborhoods, which is why I showed the boundary set as 's' on my sketch. Had the OP not already selected Rb for something else I could have used that. @sevensixtwo As I understand neighborhoods as applied to the reals, the infinity and its neighborhood arises not as an endpoint to the real line but as a result of a limiting process for such expressions as [math]\mathop {\lim }\limits_{x \to \infty } \frac{{\left( {x - 1} \right)}}{{\left( {x + 1} \right)}} = 1[/math] But you should certainly listen to uncool, analysis is much more his area of Mathematics than mine.
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Why on earth would you ask this? Why do you think I posted my last post if everything was clarified ? Specifically what is [math]\hat 0[/math] ? I ask because the very first sentence in your proof is ambiguous, and I posted my attempt to make sense of it, upto and and including equation 1. Therefore I had to choose one of the possible interpretations of your first sentence. So do you agree with my posted reasoning? Your answer will be interesting since my post is a proof of this statement.