Recent content by Carlos Gouveia

Hey, whoa. Evaluating the entropy change between two thermodynamic states is one thing. For this your step-by-step procedure above seems to be adequate. But I was talking about measuring entropy discretely -- like taking the temperature of my office as I write this, right now. How do I...

Cool. So enlighten me and tell me how this is done. Since you seem to suggest that it's a measurement I assume that this is carried out in a lab. Serious, I'm curious about that procedure.

http://physics.bgu.ac.il/~gedalin/Teaching/Mater/am.pdf

I think you can't measure entropy but you can certainly calculate it.

A nice introductory book on the FVM is Versteeg & Malalasekera's "An Introduction to Computational Fluid Dynamics - The Finite Volume Method". I have this book and I like it a great deal. Yet it may be a bit off from your niche of application. Coincidentally, I also have Hamming's "Numerical...

I got your point now. :-)

Well, in SI units h, the heat transfer coefficient is given in J/(m² s K), or W/(m² K) as 1 W = 1 J/s. Hour (hr) is not one of the SI system's base units. Therefore, k, the thermal conductivity, should be expressed as W/(m K) and in MLTΘ notation it is expressed as MLT⁻³Θ⁻¹.

Good point. Yes, the number of "times" is infinite as well. I like this answer.

I understand your point now, but I don't think that that has much to do with my original post. What I meant to say was that in the interval between 0 and 50 mph there is an infinite amount of speeds. Thus, to go from 0 to 50 mph a car should go through all those speeds, and that would take an...

What does J/Pa mean to you? To many people it might seem as meaningless as J/K at a first sight. However, J/Pa translates into volume since ΔW/p = ΔV,where W is work, p is pressure and V is volume. I think part of "meaninglessness" of entropy comes from the fact that you can't measure it as...

As far as I know, any finite non-zero number is unique. How come could it be "split into infinitely many non-zero parts"? I don't get it, sorry.

There's a difference between the 4th derivative of y (y'''') and y⁴. Since this latter is a non-linear term and being the Laplace a linear operator, I'm afraid an ODE involving y⁴ has no solution by the Laplace method. It seems to me that your problem has a typographical error.

Orodruin, I'm not sure if I understood your explanation, but if the time interval during which we have a particular velocity has length zero, then shouldn't all cars accelerate at the same "rate", or go from 0 to x mph instantaneously? I know that from definition a = dv/dt but that doesn't make...

A car goes from repose (0 mph) to 50 mph in, say, 30 seconds. Math tells us that there is an infinite amount of numbers between 0 and 50 (or between any two other numbers). Therefore, isn't it "obvious" or "intuitive" that it would take a car an infinite amount of time to go from 0 mph to 50...

Kitchen salt is soluble in water. Whenever this happens, molecules of NaCl dissociate into the two chemical entities that form such molecule, the cation Na+ and the anion Cl-. Suppose I dissolve some amount of NaCl in water. Then I pour part of this solution into another glass. Is it...