Recent content by Pollywoggy

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    Derivative *of* a partial derivative

    Thanks, I think you just answered my question :) As I was reading your reply, I was watching one of Leonard Susskind's videos and he happened to be explaining something involving the Lagrangian function and I think he also answered my question. I am going to go over that part of the video...
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    Derivative *of* a partial derivative

    Homework Statement In books I have been using to learn about the Lagrangian function, I find equations that have a derivative of a partial derivative, as in the snippet below. Is there a place where I can learn how this works and *why* it works? I think I can do it mechanically but I want...
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    What is the reason for the division by two in the angular momentum equation?

    Thanks, I knew it was something simple that I just could not see.
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    What is the reason for the division by two in the angular momentum equation?

    Homework Statement I found this in Goldstein, Poole, and Safko and have seen it in other books. What I don't understand is how the equation gets from the second expression to the third; specifically, why is the m divided by two in the last expression? I am at a loss on this but I know it is...
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    LaTeX Can't see Latex source in Linux (Firefox)

    Thanks, it seems to be working correctly for me in Firefox on Ubuntu.
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    LaTeX Can't see Latex source in Linux (Firefox)

    This is essentially what I get in Ubuntu. If I mouse over an equation, I sometimes get a "balloon" type popup showing an enlarged view of the equation and if I right click, I get the normal Firefox context menu from which I can access the source for the entire page. Other times I get something...
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    LaTeX Can't see Latex source in Linux (Firefox)

    Maybe that is the problem, that I was trying to view math in a quote box. I will keep that in mind. With some equations, I have to look for the math in the source for the entire page, with other equations, I get a Mathjax context menu and can see the math by clicking there, without having to...
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    Does dot product always commute?

    I just realized something, after posting my question. The reason the dot product is not generally commutative probably has to do with whether the vectors or tensors are orthogonal. Is that it? I think what confused me was that the book uses subscripts j, k, and l. That should not have...
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    Does dot product always commute?

    I thought the dot product was commutative but there must be something about it that I don't understand. Perhaps the dot product is commutative only for vectors and not for tensors generally? In Kusse and Westwig, p70, it says that the order of terms matters because, in general, \hat{e}_j...
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    LaTeX Can't see Latex source in Linux (Firefox)

    Apologies for having posted in the wrong place. I did not notice there was a support section. I was aware of this manner of showing the source for an entire page, but in Firefox (Linux) I can see the source for some formulas, and only the source for the math, without having to see the entire...
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    LaTeX Can't see Latex source in Linux (Firefox)

    I understand that I should be able to see the source for formulas/equations/math symbols people put in their posts, by right-clicking a symbol or equation. I seem to recall that I could do this but I am unable to do it now in Firefox (Ubuntu Linux Lucid). Is there something I need to install...
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    Learning General Relativity: What Do I Need to Know?

    I found this book and bought it a few years ago but one of the authors gave me a link to where it can now be downloaded for free: http://www.adinfinitum.no/einsteins_theory_en.html The book is in PDF format and is intended for non-mathematicians but it explains the math needed for a basic...
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    How long do structures continue shaking after quake?

    I live in northern California and there was a substantial earthquake here yesterday. To me, it seemed as though the shaking continued for somewhere between 30 seconds and 60 seconds, but one newspaper article stated the ground shook for 10 seconds. Does anyone know how long structures such...
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    Rank vs Order of Tensors | Tensor Basics

    I am confused about the difference between the rank and order of a tensor. On p 71 of Mathematical Physics 2nd Ed (Kusse and Westwig, 2006 Wiley-VCH), the rank of a tensor is described as identifying the number of basis vectors of the tensor but in some other books, this seems to be described...
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    MasteringPhysics: A Controversial Tool for Homework in Physics

    Is Mastering Physics something that is available with the purchase of certain textbooks?
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