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Re: Summary...Bournoulli for 5th Graders (LONG)



Poor Bernoulli gets the credit/blame for a lot of stuff that has nothing to do
with his law, airplanes, curve balls, and shower curtains. We went round and
round about this at our school because another teacher put this on a test and
wanted Bernoulli for the answer. When the students, who were taking lab from
me, asked me about the question I suggested the convection mechanism. To
resolve the issue, like Paul, I suggested they try hot and cold showers.
Several reported some effect with cold showers, and since then I have been
able to produce a feeble effect myself. The convection effects in a hot
shower are dramatic, especially if your bathroom is otherwise quite cold. It
works best when you first start the shower, before the whole room gets steamed
up.

Can our feeble cold shower be from Bernoulli? Bernoulli is often incorrectly
stated as something like faster fluids create less pressure than slower
fluids and any time there is a velocity difference Bernoulli is touted out.
Bernoulli is basically a conservation law and is derived under very stringent
conditions where energy and mass are conserved. However, conditions in a
shower are so far removed from the conditions for which Bernoulli's Law is
derived that I find it difficult to see how it can have anything to do with
this phenomonon.

I do love the books that still try to use Bernoulli to explain curve balls,
since they predict a curve that goes in the opposite direction from the way
curve balls actually go!