TSny's latest activity
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TSny replied to the thread I Gauss' law seems to imply instantaneous electric field.The potential at the field point ##p## at time ##t## is given by the retarded-time expression ##\phi(r, t) = \large... -
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TSny reacted to bluepilotg-2_07's post in the thread Please tell me where I am going wrong in this integral with
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Hello, thank you for the response! I should have known better, but wasn't considering even and oddness. I realize now that the first... -
TSny replied to the thread Please tell me where I am going wrong in this integral.In the second line, the first integral has an integrand that is odd in ##y##. You cannot replace ##\int_{-\infty}^{\infty}## by...
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TSny reacted to Kostik's post in the thread A Dirac's integral for the energy-momentum of the gravitational field with Like.
@anuttarasammyak Excellent! This was hugely helpful. I wish Dirac had been a little less cryptic. It's not often that one consults...
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TSny reacted to stovenn's post in the thread B Applying the Gauss (1835) formula for force between 2 parallel DC currents with Like.
Aha! I see now how I slipped up by assuming that ##\mathbf{a} = 0## implies ##\ddot{r} = 0##. I had indeed subsequently gotten the...
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There is. If you practice Einstein's summation convention a little, where repeated indices imply summation:$$A_iB_i:=\sum_{i=x,y,z} A_i...
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TSny replied to the thread B Applying the Gauss (1835) formula for force between 2 parallel DC currents.Equation (6) in the link reads $$\ddot r = \frac{\mathbf{r}\cdot \mathbf{\ddot{r}}}{r} - \frac{(\mathbf{r \cdot \dot{r}})^2}{r^3} +...
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TSny replied to the thread I Maxwell stress tensor.The last term on the right is wrong. This term should represent the divergence of just the part of ##E_{ij}## given by ##-\frac 1 2...
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I apparently passed my 15 year PF anniversary earlier this year, but only noticed just now thanks to this post :biggrin: Anyway, I too...
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Hey all. Looks like my 15 year anniversary of joining PF happened yesterday (while my internet was down). Just wanted to say thanks to...
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TSny reacted to JimWhoKnew's post in the thread I Quantum behaviour of an electron around a positively charged sphere with Like.
In addition to the wise things that were already said above, the quoted claim is simply wrong. A superposition of different energy...
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I think that as a physical process, the problem is under-determined. The constancy of ##~\left|\vec{a}\right|~## constraint...
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TSny replied to the thread Motion in 2 dimensions.Very nice explanation! I think it gets to the heart of the matter. By choosing the tangential force appropriately as a function of...
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If my calculations are correct, it is possible to construct infinitely many answers to that problem (as stated). Including "never".
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Since this problem came about as an off topic, I feel uncomfortable to hijack the thread. Even more so when the OP places a picture of a...
