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