Recent content by tomelwood

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    Linearised Gravitational Waves Derivation

    Oh of course. Thanks. OK. So now all that section makes sense, the final step is to show that the trace terms cancel out. I've been trying to find out the intermediate steps going on, and have managed to solve the equation if I can show that...
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    Linearised Gravitational Waves Derivation

    Hi A topic came up in a lecture the other day about how if certain simplifications are made, then the Einstein equation reduces to a form of the wave equation. When I look at derivations of how this happens, I get a little confused as to how this happens. I think I'm posting it in the...
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    Equations of Motion of a Solar Sail HELP

    After further investigation, I have since discovered that these are just a fairly obscure way of writing tangential and radial accelerations. However, tangential acceleration is given by Equation 286 on this page http://farside.ph.utexas.edu/teaching/301/lectures/node89.html which upon...
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    Equations of Motion of a Solar Sail HELP

    Homework Statement I am reposting an edited version of this problem from a previous post of mine, due to it not being entirely relevant to that post, and also the question was asked after the thread had been replied to, so looks like an answered question. I also aim to give more detail here...
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    Intensity of solar radiation at earth orbit

    So rather than calculating the solar constant from the sun's power, rather the power of the sun is calculated from the observed solar constant. OK. I have since discovered that I can relate the power of the sun to the intensity of the sunlight passing through a sphere of radius r, simply by...
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    Intensity of solar radiation at earth orbit

    Homework Statement I am try to understand how the value of 1370 watts per metre squared for the intensity of sunlight hitting the Earth has been derived. Is there a way to see this mathematically? Homework Equations I understand about how the intensity is related to Poyntings vector, by...
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    Composition of Quaternions as rotations

    Having investigated further, I have found that multiplying (1,1,0) by that quaternion that I didn't like does actually give (0,1,1) , but I don't understand how I can interpret that geometrically - ie about what axis and by what angle is the rotation being performed? Because the usual way of...
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    Composition of Quaternions as rotations

    Homework Statement Hi, I am having problems in showing that in practise the composition of two rotations represented by quaternions is still a rotation. The example I have constructed is: Rotate (1,1,0) by 45 degrees about the z axis. The quaternion to use is thus q = cos(22.5)+ksin(22.5)...
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    Rotations with Quaternions and their exponential.

    Homework Statement Hello, I'm trying to get my head around the various properties of quaternions that all seem very similar, but I can't quite understand the underlying differences between them. I would like to know the differences between unit quaternions, purely imaginary quaternions...
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    What is the potential function for a line integral with a vector field?

    Homework Statement I have to calculate the following line integral \int_{\gamma}y^{2}cos(xy^{2})dx + 2xycos(xy^{2})dy where \gamma is the path defined by the equations x(t) = t^{4} and y(t)=sin^{3}(\frac{t\pi}{2}) t between 0 and 1Homework Equations Now I know that the formula for calculating...
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    Finding the gradient of an integral

    Homework Statement I am getting quite confused as to the concepts behind this task. I have a function given as a double integral, and am asked to find the gradient of it. However, I have no notes on how to do this, so it is either a very simple task, or the lecturer has once again missed...
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    Integral Calculus inequalities problem

    Homework Statement Hey, just wondering how I might go about doing this problem, as I really have very little idea... Prove the following inequality: \frac{1}{e}\leq\frac{1}{4\pi^{2}}\int_{R}e^{cos(x-y)}dxdy\leqe (hopefully this reads "one over e is less than or equal to one over four pi...
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    Convergence Laws in Probability

    Homework Statement Hello, I'm trying to revise for my probability exam next week and am getting a bit hung up on how to show a sequence of random variables converges. For example, how would I got about doing this question: Let {X_{n}:n\geq1} be a sequence of random variables with...
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    Tangent and Normal Spaces, lagrange multiplier and Differentiable Manifolds question.

    Homework Statement OK I have a Differential Calculus exam next week and I do not understand about Differential Manifolds. We have been given some questions to practise, but I have no idea how to do them, past a certain point. For example 1. Study if the following system defines a manifold...
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    2-Dimensional random variable probability

    If this is all true, then the covariance is now E[(X-2)(Y-1.5)]. How on Earth do you work that out??
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