Recent content by AriAstronomer

"The geodesics in R n are the straight lines parametrized by constant velocity". This can be proved with the geodesic equation: \ddot{x^a} + \Gamma^a_{bc} \dot{x^b} \dot{x^c}=0 Locally we can find a coordinate system such that \Gamma =0 , and thus: \ddot{x^a} =0 So along a geodesic at some...

@ HallsofIvy - they still can be related. Picture yourself slowly increasing the speed of your spinning chair by pushing off from the ground at the exact same spot once per revolution. That would be analogous to running I think.

Hey, Got into a discussion with my friends over this: If you spin in your chair clockwise, since the Earth spins counterclockwise, as you start spinning by conservation of momentum the Earth would also start speeding up. Then, frictional dissipative forces from the air would slow you down to a...

Hey everyone, So I've been killing myself trying to find a good reference that talks about the wavelength dependence of dust grains when the size of the grain is about the size of the incoming light, or s~lambda. I have numerous references for when s<<lambda (absorption dominates with a...

Hey everyone, So I'm doing a bit of research on transition probabilities for a presentation, and it seems like, from checking different resources, that in the atomic nucleus the process of transition rates to describe the rate of emission/absorption between 2 energy levels is used...

Homework Statement Find the moment of inertia tensor of the plate attached below Homework Equations σ = area density The Attempt at a Solution So the main problem I'm having is solving for Ixx and Iyy: 1) Ixx = σ∫∫(y^2 + z^2)dydz, since there are no dz components, I don't see how...

Yeah, your right, the sign is wrong. I understand that the equations of motion are based on the derivatives, and thus all constant terms are thrown out, but I assumed that if the question asked for the Hamiltonian and no further, that these constant terms would still be included. If it doesn't...

Homework Statement Particle of mass m constrained to move on the surface of a cylinder radius R, where R^2 = x^2 + y^2. Particle subject to force directed towards origin and related by F = -kx Homework Equations L = T - U H = T + U The Attempt at a Solution So I have the solution, but...

Ahhh crap. Yeah makes sense. I stupidly assumed that L and T must correspond to the same frame, but whoever is making the measurement is T... Thanks.

Sorry for the non-latex. I'm looking at a definition right now for special relativity, and it says [ tex ] t = \frac{ \tau}{\sqrt{1 - \frac{v^2}{c^2}}} = \gamma \tau [ /tex ] where tau is proper time. Thus, by using this method, \gamma = 5/3, t = 5/3 \tau, or \tau = 3/5 t. Thus, (where L =...

Homework Statement The question goes: A meter stick with a speed of 0.8c moves past an observer. In the observer’s reference frame, how long does it take the stick to pass the observer ? Homework Equations Special Relativity: where T and L = proper time/length, t, l are not: t =...

Hey everyone, So unfortunately I haven't taken Stat Mech yet (and my GRE is in a week), but through casual reading and forums I've gathered what the concept of fermi temperature and energy is...or thought I did. From what I understand, below the fermi energy (the fermi energy within an atom...

I'm looking at it, but judging from the diagram it looks like dBz should equal cosine theta, not sine theta which is what they're claiming... Still kind of confused.

Homework Statement Find magnetic field along the z-axis of a circular loop, radius R with constant current lying in the z=0 plane. Homework Equations vec(r) = vector of r. zhat = unit vector z. The Attempt at a Solution So starting with the definition, B = (u_o I/4pi) (dl x...

Ahh Power/Volume. Thanks. I had seen this claim on a flashcard, I'm preparing for GRE's and got a bunch of flash cards sent from a school to help me. Must be a typo on their part then. Ari