Recent content by Ksitov

Thank you for your reply. I knew these quantities but I'm speaking about equations. Why EDP are always in term of second derivatives ? (diffusive - convective - wave equations) Even in General Relativity, Riemann curvative tensor is "the derivative" of the Christoffel symbols which is "the...

Dear all, I'm asking why there is no higher derivative than two in physics ? I never encountered a third (time or space) derivative in physics. Have you some litterature about this? Thank you. Regards.

Good evening, So... I am looking for the Tungsten permettivity and i don't find this feature... I have searched on Wikipedia, some material data but i don't find... Do you know what is the Tungsten permettivity? Thanks.

Hi, I'm doing a 1D thermal conduction simulation on Comsol Multiphysics 4.4 and my first component is vacuum. I did'nt found the vacuum in the material list. Should I create a new component with a null thermal conductivity ? Thanks

Hi, Why not? To find the electrostatic force, i think (and I'm sure), the mass is'nt necessary. But maybe for the time of oscillation no? I don't know. So... You should to read Richard Feynman's books.

You can notice x^3 - 1 is of the form "a^3-b^3". You can factorize ;) ! And you can factorize: 4x^3 + x. It is a partial fraction. Good luck ;) !

Hi. Use this relation: F = G*m*M/d² Here: - m is the mass of satellite. - M is the mass of the Earth. - d is the distance between the center of the Earth and the Satellite. - G is the gravitationnal constant. Warning for the distance ;) ! Good Luck.

Hi ! I agree with Y must be a e^(+) (positron). Because with Soddy's Law you have: For protons: 9 = 8 + Y + 0 <=> Y = 1 And for nucleons you have: 17 = 17 + Y + 0 <=> Y = 0 It's a positron ! Try to use my method. Good luck ! :D

Hi, I'm okay with your result. I don't think that you can simplify. If you look for the variation's function, it's not necessary ! (e^(-x))/(1+e^-x)^2 Because: e^(-x) > 0 and (1+e^-x)^2 > 0

For exemple, in my classe we have in Physics: - Mechanical Wave - Radioactivity and Nuclear Energy - Mechanical of Newton and harmonic oscillator - Electricity (RC, RL, RLC) - A little Physic Quantic (very little...)

Oh ! Game Over xD ! g o h = g ( h(x) ) g ( h(x) ) = 1/h(x) = 1/x² Do you understand?

But he writes: fg and not f o g. And he has just start to learn functions.

Hi everybody ! I'm French and I have any questions. - What is the program of physics at the high school? (In USA) - What is the program of mathematics at the high school? (In USA) I'm new on PF and I'm very interesting by Physics. I go to a english's forum because I want to learn to speak...

I think here it's: fg = f(x) * g(x)

Say we what do you find ;) !