On Fri, Jul 15, 2011 at 4:25 AM, Joshua Cude <joshua.c...@gmail.com> wrote:
> > > On Thu, Jul 14, 2011 at 5:52 PM, David Jonsson < > davidjonssonswe...@gmail.com> wrote: > >> Hi >> >> Can someone help me to derive the spring constant between water molecules >> based on the bulk modulus of water? It seems simple but i just >> can't figure it out. >> >> How does spring constant between water molecules in >> F = - k x >> relate to the bulk modulus >> K = - V dp / dV >> >> k = spring constant >> F = force between molecules >> x = elongation of spring or displacement of molecules relative each other >> K = bulk modulus of water = 2.2 MPa. It describes the pressure needed to >> make a relative volume change. 1 % compression requires 22 kPa, 10 % >> compression requires 220 kPa, etc. >> V = Volume of the fluid >> dV = volume change due to pressure >> dp = pressure change causing volume change >> >> This is a general question for all fluids and not only water. It has >> vortex and rotation applications. I will show you later. >> >> David >> >> David Jonsson, Sweden, phone callto:+46703000370 >> >> I don't know that a simple model like springs connecting the molecules > works for a liquid, but here's a way to connect the concepts: So what would be used then? Thanks for your contribution. What I actually is trying to determine is to find the speed of the molecule in specific directions. If I have the spring constant then it is easy to determine the temperature. And as you can guess from earlier postings I will determine centrifugal effects based on these velocities. A ball park estimate is that it is just a little lower than for gases at the same temperature. Assume that the speed i gases is the same for fluids and solids. When the molecule is in the middle when the spring potential energy is zero all energy has to be in the kinetic energy of the molecule and thus be the same as for gas molecules when they fly freely without collision. And the means speed of something in periodic oscillation is the maximum speed/2^½ ~ 0.7 of the max speed and mean RMS speed is 0.5 of max speed. This means that the variations in vertical acceleration for molecular motion (the Eötvös effect) has the same formula as for gases but with proportionality factors of 0.5 or 0.7. The tangential effect is still under investigation by me and I currently investigate two or three alternatives. The Eötvös effect on atomic and molecular motion is very interesting. It means that water and rock on Earth weighs 0.04 % less than their mass. This should be detectable. The effect is proportional to the temperature. Imagine the effect on hotter places like the interior of planets and stars. Good. The problem appeared to be somewhat simpler than I first thought. It is interesting to see that centrifugal variation is independent of the oscillation frequency of the molecule. I really needed this since I will present the results in less than three weeks:-) I think the model error is less than 2% based on the difference between isothermal and adiabatic bulk modulus, found here: http://physchem.kfunigraz.ac.at/sm/service/water/H2Obetat.htm Greetings from the Bergian Garden in Stockholm, David
