Recent content by AmirSafavi

Lets think of motion on a plane for now, so \tau loses its vector properties. Think of a force applied on a particle moving it a an infitesimal distance ds. Then we can say dW=Fds. If you think of the torque instead, about some point (doesn't matter here for such a small distance), F=\tau /...

true. well actually, \vec{\tau} = \vec{r} \times \vec{F} I think the best way to learn this rather confusing subject matter is to start out with a good book, i.e. Introduction to Mechanics, by Kleppner and Koleknow and see how all of these values are derived. That's how I've learned and...

It's been proven wrong :D

A very timely post indeed. This paper: http://arxiv.org/abs/math.NT/0405509 seems to prove that it is infinite. (very new paper)

why it is 75 Hmm... #2 is fairly simple. I'll write my solution as a good LaTeX practice... \log_{4a}40\sqrt3 = \log_{3a}45 \frac{\log40\sqrt3}{\log4a} = \frac{\log45}{\log3a} \frac{\log40\sqrt3}{\log45} = \frac{\log4a}{\log3a} \log_{45}{40\sqrt3} = \log_{3a}{4a}...

"Have you read up on the method of undetermined multipliers yet?" By undetermined multipliers do you mean lagrange multipliers / constrained optimization?? If so, I know everything they're teaching us here in first year calculus. i.e. very little I'm thinking I'll learn some more...

Ok thanks a lot for the replies. I get what everyone is saying. The trouble I have then is with Landau's use of \frac{d}{dt} \frac{\partial L}{\partial \vec{v} } = 0 (on page 5) when he clearly defines \vec{v} = \dot{\vec{r}} Because according to the whole generalized...

I'm with Integral too. There is absolutely now reason why placing a magnet near a receiving antenna should cause it to vibrate. The antenna is after all just a piece of metal. Even if you were talking about a 50 Watt transmitter, there still would be no vibrations, due to the extremely high...

I don't think I was clear Hi, Thanks for the reply. I don't think I'm being very clear. What I'm trying to say is, \vec{v} = \dot{\vec{r}} now, let's say, in spherical co-ordiantes, \vec{v} = dr/dt\hat{r} + rd\theta/dt\hat{\theta} + r\sin \theta d\phi/dt \hat{\phi} what...

Hi all, I'm trying to understand something about the lagrangian. My resources for learning a currently limited to Landau's mechanics and anything which is on the internet. L = L(q,\dot{q},t) Now, here is a simple question: what are these generalized co-ordinated exactly? For...

thanks for the reply Hi DrDick Thanks for the quick reply. I'm glad there finally seems to be a place where I could ask questions regarding physics. Actually I'm not all that educated myself. I'm a junior EE undergraduate at a good Canadian university. I'm good at math and have basic...

Hi, I just joined physicsforum.com and have a great interest in physics. Looking at the previous posts here, there seem to be a huge amount of variation in the quality of posts here. The membership here seems to be polarized between people whom I would call illiterate (affectionately...