Recent content by ozymandias

I've never seen an artificially made fabric that didn't have a better, natural counterpart.

While it's true that a high price doesn't guarantee quality, the opposite is almost universal: cheap means lack of quality. Cashmere, e.g., is rare and hence expensive. High quality workmanship is expensive. It's like anything else in life. As for the original shirts, they are hideous. The guy...

I'm not a big fan of Griffiths, but his "Electrodynamics" text has a pretty good derivation of it in chapter 10 - self contained and quite intuitive. ----- Assaf http://www.physicallyincorrect.com"

Amazing solution, thanks for sharing it. So is squaring the "connections matrix A" a common trick in graph theory? What sort of things can you learn from it?

In terms of danger to living beings, high voltage isn't intrinsically dangerous. A Van de Graaff generator can easily create potential difference of thousands of volts and more, and yet is safe (although I wouldn't want to touch a charged one!). It's the power (P=I^2*R=V^2/R) that fries you if...

@RockFreak, What was your friend's reasoning? ----- Assaf http://www.physicallyincorrect.com"

Argh, the suspense ... can you ask the person who gave you this question? I've got to know the answer! :smile: I've tried googling the problem but all I could find is Ramsey theory, which is definitely not what we're looking at. ----- Assaf http://www.physicallyincorrect.com"

Curses, you've infected me with this now too! :smile: I'm not sure how to solve it, but here's a thought. Say there are N people. Pick a person X. X knows 22 people and doesn't know M people. Note that M+22+1=N. Let's call the group of people X knows A (having 22 members), and the group of...

I can't help you with the off-center field, but there is a closed form solution for the on-axis field. It's axial (for obvious symmetry reasons) and equal to (in SI units): B_z(z) = \frac{\mu_0 n I}{2} \left( \cos(\alpha_1) - \cos(\alpha_2)\right) where alpha_1, alpha_2 are the angles...

I found it in the library in my first ever semester at uni. Ah, the memories :). It's known for its extra-tough problems. If you can solve all of them, you can easily get into an honors class, I think. I personally think it's superb, but it's not easy. Another good book to have is David...

Smells like Kleppner & Kolenkow to me ... :) It took me a while to zero in on it because it's so subtle. Your horizontal force equation is the problem. There shouldn't be a -mA there. x is the distance to the mass as measured in an inertial system (and NOT from the wedge's origin), and...

Nabeshin, your argument works the other way too. For a circular orbit, a = v^2/r (that's universal, nothing to do with gravitation). Plug in v=\omega r = \frac{2\pi r}{T} and obtain a = \frac{4 \pi^2 r}{T^2} On the other hand, from Kepler's law, T^2 ~ r^3, so F = ma \propto \frac{4 \pi^2...

Regarding Kleppner & Kolenkow, the correct pages are 260-2, not 262-4, so it seems it's my mistake. However, on p. 263 they state and reason quite clearly that "rotational motion about the center of mass depends only on the torque about the center of mass, independent of the translational motion...

You can find proof in Kleppner & Kolenkow (pp. 262-4) or David Morin's book (pp. 380-1).

Hi everyone, I'm sure most of you are familiar with the "put a bell in a jar and pump the air out until you can't hear anything" experiment undergraduates are shown (e.g. see http://www.teralab.co.uk/Experiments/Bell_in_Vacuum/Bell_in_Vacuum_Page1.htm" ). Now, the "classic" explanation is...