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Re: [Phys-l] "Flow"



A unit * of water + a unit of meths doesn't = 2 units of liquid.

There's a vitamin in eggs and a protein in white, which binds to the vitamin and prevents absorption; fortunately cooking "kills" the protein. Furthermore, I suspect there's an excess of that protein, so eating raw eggs will probably result in a vitamin deficiency disease.

bc


* volume, of course.

Michael Edmiston wrote:

John D. said,
"The flow of ideas is a fine example of _nonconservative_ flow."

Yes, I almost mentioned that in my last message, but was trying to keep the message short.

It seems to me that having examples of nonconservative flow for comparison to conservative flow is good thing to help students see the difference. Since physics examples often involve momentum and energy-mass transfer/flow, students might see everything as conservative and wonder what the big deal is. I use "news" (or as John says, "flow of ideas") as an example of nonconservative flow.

I think there is a similar situation with the superposition principle. It happens so often that students wonder if there is anything that doesn't follow the SP. Are there truly cases where "2+2 comes out 3 or 5?" Some examples sort of exist in biology. Calcium supplements can be good for you if you need extra calcium in your diet, and the antibiotic tetracycline is good for you if you need it to fight an infection. So if you take them together you get both benefits, right? No, because the calcium binds to the antibiotic and neither of them get absorbed from your intestines. You can end up with "2 + 2 = 0" A good name for this is suppression. The opposite is synergism like you get when you mix alcohol and barbiturates... "2+2 = 6," that is, way more than you bargained for. These are not perfect examples because they deal with two different things adding, but it gives students the idea that there are times when the sum of two things turns out less or more than you expected. That makes superposition seem a little more special just like knowledge of nonconservative flow makes conservative flow a little more special.

Michael D. Edmiston, Ph.D.
Professor of Physics and Chemistry
Bluffton University
Bluffton, OH 45817
(419)-358-3270
edmiston@bluffton.edu

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