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    News Be optimistic about America

    Here's an interesting quote I read recently that has to do with this: “Those who fail to exhibit positive attitudes, no matter the external reality, are seen as maladjusted and in need of assistance. Their attitudes need correction. Once we adopt an upbeat vision of reality, positive things...
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    The Secret on how men can attract women

    I've heard it being included in girls' top 3 things a couple of times. One girl in particular that I thought I liked in college was very fervent about it.
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    Chemistry How many moles.

    If you have one mole of the compound, and if there is one atom of magnesium per compound, then how could you have anything other than one mole of magnesium?
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    First year undergrad - will chemistry be useful?

    I would just take some kind of a basic, chemistry isn't really a course that provides the foundation for anything in physics so there's not really a reason to get to it early. It's not getting you into some sequence early so that you can then take a multitude of advanced courses as a result...
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    Career prospects with either EE or CompSci

    heheh, your priorities are correct. It was once that people were debating which majors were better for the pay, now people are simply debating which major actually provides a real job! Heh, both computer science and electrical engineering are great, and from my experiences in life, they're...
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    First year undergrad - will chemistry be useful?

    I would take basic chemistry later in your degree, as it will be a nice simple break from your more difficult physics courses, though you need to budget the time for the busy work that is 90% of your time dealing with chemistry labs. Further, after you have a foundation in basic physics and...
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    Programs Electromagnetism for an Electrical Engineer Major?

    I used the Griffith's book for electrodynamics for my physics undergrad. After finishing the course a year later I ended up tutoring a good friend who was doing the equivalent electrical engineering course. I went over antennas, transmission lines, waveguides, and plane waves at dielectric...
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    Meteorite crash in Russia

    heh, the quote in that asteroid picture reminds me to check Neil Tyson's twitter..
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    Electromagnetic Induction

    According to the beginning of this episode of the Mechanical Universe, this situation was a starting point for Einstein's special theory of relativity (fast forward to 1 minute 22 seconds):
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    Mole, Molar mass and Avogadro's number

    Well, grams are what's important in the macroscopic world of the humans, so we want to discuss masses of things in grams. However, if one were to label the masses of the various elements of the periodic table in terms of their weight in grams, there would be a nasty 10^{-23} factor on all of...
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    Capacitor help needed (voltage needed and time constant question)

    For part one you're simply using Q = CV where 'Q' is the charge of the capacitor, 'C' is the capacitance, and 'V' is the voltage required to do so. To get the electric field from the spacing and the voltage you just need to use the equation E = V/d (E is the rate at which V changes with...
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    Favourite Quotes

    Thanks, heh, it was a good one. Also, everyone should check out or remind themselves of the great Howard Zinn today:
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    Favourite Quotes

    "Freedom isn't free. It shouldn't be a bragging point that 'Oh, I don't get involved in politics,' as if that makes someone cleaner. No, that makes you derelict of duty in a republic. Liars and panderers in government would have a much harder time of it if so many people didn't insist on their...
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    Simple time-independent non-degenerate quantum perturbation

    Ok, that definitely cleared everything up. Thank you for everything, I especially wouldn't have guessed that they were expanding corrections to the eigenstates in terms of unperturbed eigenstates. Wow, you'd think that would have been a part of the derivations they would have spent more than...
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    Simple time-independent non-degenerate quantum perturbation

    I'm reading through this pdf ( on simple quantum perturbation theory and I'm quite confused with equations 32 through 34. They have E_{n}^{(2)} = <n^{(0)}|V|n^{(1)}> = - \sum_{m \neq 0}{\frac{|V_{mn}|^{2}}{E_{mn}}} but I would have done E_{n}^{(2)} =...
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    Use of spherical unit vectors

    Yeah, basically if you write <r, 0, 0> it looks particularly deceiving. With this notation you're used to assuming that each variable is in reference to a scalar multiple of the same vector that never changes. If you write this expression out you have <r, 0, 0> = r \hat{r} + 0 \hat{\theta} + 0...
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    Use of spherical unit vectors

    Another way to put it would simply be to say that \hat{r} changes direction depending on where you are in \theta and \phi. Thus you need the information of all 3 because otherwise you don't know the exact nature of \hat{r}.
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    Optics | Electromagnetic Waves | Electric/Magnetic Fields

    The flux density at r = 1m (which you have correctly calculated) is the time averaged Poynting vector at r = 1m. So how is the amplitudes of E and B related to <S> (the time averaged Poynting vector). Also recall that the amplitudes of E and B themselves are related to each other, so you can...
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    What are the important lessons in linear algebra for Quantum?

    You need to understand vector spaces and transformations between different vector spaces (matrices). You're going to be told in quantum that quantum systems are defined by "abstract vectors" and to find out something about the quantum system (such as the momentum of a particle), you're going...
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    Sum of work = Work done by net force

    The answer is yes, you're correct (about everything).
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    Basic mechanics question

    Firstly, you get to make an arbitrary choice of where the 'x' and 'y' axes point. This is because vectors are physical objects that are independent of the choice of coordinate systems used to represent them (indeed this is the entire reason why we use vectors in physics instead of just...
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    Basic mechanics question

    Use vector addition. Break the two vectors you are dealing with into their 'x' and 'y' components and then add them together. Use the relation \theta = \arctan{(\frac{y}{x})} to get \theta for the resultant vector and the magnitude ('M') is just x^2 + y^2 = M^2.
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    Math or Computer Science?

    Sounds like a recipe for a major in computer science with a minor in mathematics! I highly recommend this route, you'll thank me when you get near guaranteed job opportunities after your undergraduate degree in the private sector. Majoring in math with no computer science will make life after...
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    News Should David Gregory be Prosecuted

    Post of the year. Everyone should have discretion. "He who joyfully marches to music rank and file has already earned my contempt. He has been given a large brain by mistake, since for him the spinal cord would surely suffice." - Einstein Replace the military reference with not using...
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    Graphing Covariant Spherical Coordinates

    You're right, woops, although the contra and covariant basis vectors are all in the same direction for orthogonal coordinate systems their magnitudes are inverse of each other. I was just kind of being optimistic that you might have seen different crystal lattice types that you can then...
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    Schrodinger equation help

    So you have the integral:\int{\psi \psi^{*} dx} = \int^{\frac{L}{2}}_{\frac{2L}{3}}{\sqrt{\frac{2}{L}} \sin{\frac{n \pi x}{L}} \sqrt{\frac{2}{L}} \sin{\frac{n \pi x}{L}} dx} = \int^{\frac{L}{2}}_{\frac{2L}{3}}{\frac{2}{L} \sin^{2}{\frac{n \pi x}{L}} dx} You can get the integral of sine squared...
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    Graphing Covariant Spherical Coordinates

    I didn't think there was a difference between the contravariant and covariant spherical basis vectors because they're orthogonal even though they are positionally dependent. If your mission is to mess around with covariant basis vectors in 3 dimensions (in a visual geometric way), in solid...
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    Finding X,Y points on a Circle

    It's x^2 + y^2 = 10^2. You can do (x - a)^2 + (y - b)^2 = r^2 for an arbitrary center point (if the circle is not centered at the origin). In such a case the point (a, b) is your center and 'r' is your radius value.
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    Medical Can't sleep, thinking too much.

    It could be a symptom of anxiety, not that you're staying up thinking about things you are anxious about, but I believe the brain chemistry of the condition "anxiety" often leads to being more talkative at night, a night person, thinking heavily at night preventing sleep, etc. I'm not saying...
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    Density of power of Antennas?

    You weren't given what type of antenna this is? Each antenna has its own distinct equations for V, A, E, B, S, <S>, and P. You should be able to find the power density (time averaged Poyting vector) at 10m by solving your equation for E at 100m (using your known value of E = 250) to obtain...