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Hi see the attached picture... 2 coupled masses, each suspended from spring in gravitational field... also entire construction can vibrate only vertically... I need to write lagrangian for this system in the following form: [math] L = \frac{1}{2}\sum_{i=1,j=1}^{2}m_{ij}\dot{x}_i\dot{x}_j-\frac{1}{2}\sum_{i=1,j=1}^{2}k_{ij}x_ix_j [/math] [math]x_i[/math] and [math]x_j[/math] are displacements of masses from equalibrium positions and springs are identical the kinetic part of L is easy one but i stack with potential part... i get to this expression(i always confused about right signs): [math]m_1g(l+x_1)+m_2g(l+x_1+l+x_2) + \frac{1}{2}m_1{x_1}^2+\frac{1}{2}m_2{x_2}^2[/math] - positive direction taken along g direction - l is length of unstreched spring every potential term in L must in [math]k_{ij}x_ix_j[/math] form but i don't see a way how do i get it from my expression for potential energy because there are g force terms containing only [math]x_i[/math] or [math]x_j[/math] thanks

thanks, on it...

i meant to say high-speed photography ok i will look for this term on google

ok i try this thanks:)

anyone knows links to slow-motion movies? like bullet fly OR water bounces of the wall OR explosion expansion and on the same breath... anyone knows some interesting science-fiction movies? thanks

i searched the forum for MooeyPoo posts, i looked at the titles but didn't looked into threads(too many of them) but no luck... and i did google also. i found some links collections for pre-recorded and online transmission but nothing like online/realtime lectures not even the pre-recorded

hi anyone knows any realtime (live) internet tv transmitions about physics , mathematics and etc? thanks

hi anyone knows program for plotting domains of complex variable? such as: 1<|f(z)|<=3 or |arg(z)|<(Pi/4) or even something like this one: f(z)=z^3, |z|<=2, Im(z)>=0 thanks

here is wave equation: I know that any function of x-ct variable will solve the above equation, where c is wave velocity. Below is an example of wave written as wave packet with Ai - Airy function. the first part of equation describes propagation of wave' envelope with group velocity and second part, Airy function, describes propagation of wave itself with phase velocity. I noticed that both parts can't be written as part1(x-Vg*t) and part2(x-Vph*t) .... so are these parts still represent traveling waves? If so then is it true that any function f(x,t) with x appearing only once in power 1, will describe travelling wave? thanks

If you are not serious about programming and gonna drop it after a month so don't waste your time - learn VB or VB.net... if you are serious but you are interested in learning programming for very specific subject you probably better to find out what this subject reqieres like math,graphics and etc. and only then make choice... finally if you seriously interested in general programming then go straight to C/C++ without wasting your time on languages like VB,Pascal,all sorts of Scripts and etc. I think it's general mistake that people say that VB is easier that C++. When you'll want to make a more complex app, not just stick two buttons and textbox on the form, VB will give a real headaqe. I know that because I tried VB myself to see what's so easy about it... And this is not true at all that you need write hundreds lines of code in C/C++ just for showing windows. It is enough just 10 lines.

but there is so much data collected before earthquake happen .... so if calculations or simulations are too complex and chaotic to be done why then stastical methods don't work? at least it could give us some time range...

would you please explain a little further? Why these forces can be measured? What are the parameters that can be measured?

i'm not a professor or doctor first of all... but from what i learned until now the question of duality of physical phenomena is connected to inability of math to give uniform description for phenomena. The example i have in mind is that of a light of different wavelength. As long as wavelength not too short (like visible light) the light interacting with matter can be seen as wave but when wavelength is shortens (frequency grows) the mathematical description of interaction must consider the light to be particle-like So the bottom line is that i think that probably the true mathematical description of a light is not as wave or as particle but something else.... something that should combine these two sides wave-particle under the same hood. So basicly the question of duality will resolve after some time... will be glad to here where i wrong...

I want to undestand why earthquake can't be predicted even very short time before it happens?