Recent content by mingshey

  1. M

    Help with Young and Freedman 11.76 Problem

    I'd think about the free-body diagram for a single beam in that position and angle hanging idly in the air just with the thread. Then the forces would be the gravity and the tension of the thread Next, at the hinge the two beams are in a symmetrical configuration and the forces they exert on...
  2. M

    Relativistic de Broglie Wavelength

    Comparing this with the non-relativistic phase velocity: E={p^2\over 2m} v_{ph} = {\omega\over k}={E\over p}={p\over 2m} = {1\over2} v_{particle} v_{gr} = {d\omega\over dk}={p\over m}=v_{particle} The relativistic phase velocity does not converge to the non-relativistic one even then the...
  3. M

    Current density and theorem of curl of curl

    Thanks Thanks, George. I couldn't think of number 4). Thanks to you Malleus, too, for your hand of help. It was the easy part but I diffused the point there. Sorry. ;)
  4. M

    Current density and theorem of curl of curl

    Jackson("Classical Electrodynamics", Ch.6) uses the theorem of curl of curl to separate current density into transverse and parallel, \vec J = \vec{J_p}+\vec{J_t} to say, \begin{align*}\vec{J}(\vec{x}) &= \int\vec{J}(\vec{x'})\delta(\vec{x}-\vec{x'})d^{3}x'\\ &=...
  5. M

    Line tangent to an elipse given one point

    Given a formula for an ellipse, {x^2\over a^2} + {y^2 \over b^2} = 1 and a point Q(x_1,y_1) outside of the ellipse, to find the point of contact P(x, y) on the ellipse: There's an intuitive solution and a solution using differentiation. I'll show you the differentiation version and then...
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