Recent content by tomeatworld

Homework Statement The conductivity of a plasma is defined as \sigma = i\frac{Ne^{2}}{m\omega} where N is the electron density. a) Prove the refractive index is: n = \sqrt{1- (\frac{\omega}{\omega_{p}})^{2}} with \omega_{p} = \sqrt{\frac{Ne^{2}}{m\epsilon_{0}}} b) Show the Attenuation...

Ok, thanks! Sorts everything out I think!

So using the pericentre (is that the right point?) you can get the closest approach to the black hole. Then assuming a sphere get the volume etc etc. I used the semimajor axis in a).

The 8kpc is for the Suns orbit. How can you use that for S2's orbit?

Just added an edit. We are told to assume the distance to galactic centre is 8kpc. Ok. Very silly of me. Worked it out perfectly. Thanks for the push in the right direction! I can't however work the second bit out. It's wanted in M_{SUN} pc^{-3} but I just don't know where to start.

Homework Statement By mapping the star S2 close to Galactic Centre, the orbit is found to have a semi-major axis of 0.119 arcsec , an inclination of 46^{o}, an orbital period of 15.2 years, an eccentricity of 0.87 and a pericentre separation of 0.0155. a) Estimate the mass of object at the...

I'm not sure what you mean? Surely, it just has 10pc put into it.

Homework Statement By comparing with the luminosity of the Sun, calculate the absolute magnitude of a 60W lightbulb. [THe absolute magnitude of the Sun is +4.75; you may ignore colour differences] Homework Equations m-M=5log(d/10pc) f = \frac{L}{4\pi d^{2}} m1 - m2 = -2.5long(f1 / f2) The...

I'm not sure I understand. How can the close encounters of galaxies cause the creation of different typed galaxies. As a guess, I'd think that maybe the close encounters will cause the slowing of (any) rotation and so elliptical galaxies.

Ok, I can't find the page again, but it read something along the lines of "random close encounters play a much greater role in the evolution of galaxies than stars". I was trying to work it out, but would rather have someone who knows what it means help!

So I was reading through a textbook and came across the term 'close encounter' but no definition or explination of what it means. From what I can make out, I would assume it's referring to asteroid interaction with young galaxies and the role in forming galaxies and stars but this is all...

Homework Statement For the circuit below (attached) plot the amplitude of AC voltage across resistor as a function of the angular frequency of the ac source. Homework Equations ZR = R The Attempt at a Solution I'm not really sure about any of this. Across the resistor, the complex...

Homework Statement If A=[{5,3},{-2,-2}], find the eigenvectors of A. Using these eigenvectors as matrix P, find P-1 and thus prove P-1AP is diagonal. Homework Equations None The Attempt at a Solution So i can get the eigenvectors to be <3,-1> and <1,-2> corresponding to eigenvalues 4...

Ok, thanks for the help!

Great. So do programs like mathematica choose them at random or is there a reason it chose <-1,2> over <1,-2>?