Recent content by DreadyPhysics

Point taken, "flux" was a poor choice of words. A further point in the thread that the second law only applies to reversible processes is also an important distinction. This thread has been very helpful, and I might return with more questions shortly.

I get that heat won't leave or enter the piston, thanks to its adiabatic walls. But will friction within the system generate heat (as it generates entropy?) I suppose it must- but then Δq must refer to heat entering or leaving the system; a heat flux if you will (as ΔS would be an entropy flux.)...

Thanks guys, that actually helps a great deal. I'm still unclear on the distinction between adiabatic and reversible, though. It would seem to me that all adiabatic processes have to be reversible (if done slowly, I guess) in the sense that Δq = 0 by definition, so ΔS=0 by definition, and as...

I'm trying to resolve some of my conceptual sticking points with the Carnot cycle. For one thing, I'm reading Reiss's Methods of Thermodynamics, and he offers a proof that the Carnot cycle obtains maximum efficiency when conducted reversibly. How can the cycle be conducted reversibly? During...

Well it would be nice to have some reference to those reasons :)

But cannot a single atom rotate on its own axis like a top?

When using the equipartition theorem to derive the heat capacity of an ideal gas, you have \left\langle H \right\rangle=\left\langle \frac{1}{2}m\left(v^{2}_{x}+v^{2}_{y}+v^{2}_{z} \right) \right\rangle and each degree of freedom contributes 1/2 kT to the total energy and 1/2 k to the total...

Well, to be precise, Descartes definitely believed in an external, physical, "real" reality independent of our consciousness. He was a materialist in this sense. A different school of thought, the idealists, holds that consciousness *is* reality and there is nothing outside of it. Berkeley...

Excellent, that answers my question. Thank you very much.

Hi All, When computing the commutator \left[x,p_{y}\right], I eventually arrived (as expected) at \hbar^{2}\left(\frac{\partial}{\partial y}\left(\frac{\partial f}{\partial x}\right) - \frac{\partial}{\partial x}\left(\frac{\partial f}{\partial y}\right)\right) and I realized that, as correct...

Isn't that kind of hard to say, though? I agree in general that there should have been some force to set the blob in angular rotation... But I just don't know enough about cosmology to say for sure. We're talking about which universes are possible and which are impossible.

This is interesting, I've never heard of it. Was Mach correct in his deduction? It seems like a pretty bizarre way to think of inertia. Is there any sort of modern discussion of this thought experiment? Don't leave us hanging!

In the case where you see the truck standing still and the Earth as rotating under it, to make this frame of reference work you have to see the truck as standing still and the entire rest of the universe rotating, including the box. Hence it would move.

That's a good point, lenfromkits, but there are plenty of other observations (unrelated to galaxy rotation curves) that support the notion of cold dark matter. Gravitational microlensing, for instance, has been used to map specific distributions of dark matter. However, I don't have the time or...

Not all atoms will contain Neutrons. Hydrogen especially, being the lightest element, has "no need" for Neutrons in its nucleus (although it is possible, just unlikely, as Dr Lots o Watts pointed out.) As you move down the periodic table to heavier elements, isotopes (variants of the element...