Getting back to the original question, with some extensions in the context
of recent postings:
First of all, it is a fact! My wife can dull my double-bit Gillete razor in
one application and prevent me from getting the usual 30 days out of it. I
finally asked her why this was so, and she told me it was because women
shave with an upward stroke (I guess this means against the direction of
hair growth) and men shave with downward strokes (although I use both --
down first and then up). But the interesting thing is that for years I
would hand over my 30 day old razors and she would happily use them for
another 30 days (She cannot tolerate a brand new blade for the knicks and
cuts). If she got a new one by mistake, she was unhappy -- and I had to
typically throw it away after just one uncomfortable shave.
But the shallower physics of the situation is that while shaving, I could
hear a persistent note from the hollow handle! So I blew across the open
end and there was the same note. From this was born a student lab activity
after I has saved up enough razors. I would use needle-nose pliers to pull
out the fangs, write a number on the handle, and pretend that each was
different (some were beige and some were blue, and some seemed a different
blue). Dave Vernier's Frequency Meter software on the Apple II was the
first way we tracked the "note", and with vernier calipers dimensioned the
cavity. Ostensibly to find the velocity of sound, we made the usual
end-correction and calculation. When things did not turn out quite as
expected, we reasoned that maybe the antinode at the end was inside by the
amount of the end-correction rather than outside because of the way we were
blowing the tube. This seemed comforting, but did not convince Tom Rossing,
who pointed out further that the bore was in fact conical, since it is not
an extrusion and needs some "draft" to release the mold. We left the
project at the point where it was obvious that the air temperature was
warmer than that of the room, and we would need to imbed thermistors or
thermocouples to track that down.
But I still hear that note in the quiet of the morning, and I still don't
know why women, who probably use just as much "softener" as men do, can
dull a blade so badly with just one application. As our daughters grew
through this same sample period, it seemed that age and experience were not
a factor.
Tom Ford
Product Development
The Science Source
Manufacturer of Science Educational
and Design Technology Equipment
P. O. Box 727
299 Atlantic Highway
Waldoboro, ME 04572-0727
(207) 832-6344
1-800-299-5469
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e-mail: tomford@thesciencesource.com http://www.thesciencesource.com