

The Ancient Mechanics and How They Thought - robg
http://www.nytimes.com/2008/04/01/science/01clas.html?ex=1364702400&en=a5c381a7a499a498&ei=5090&partner=rssuserland&emc=rss&pagewanted=all

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Alex3917
“Think of the oar as a lever,” Prof. Mark Schiefsky of the Harvard classics
department said. “Think of the oarlock as a fulcrum, and think of the sea as
the weight.”

This is false. An oar is a second degree lever, meaning the fulcrum is
somewhere along the shaft a few inches above where it meets the blade.
Thinking of the oarlock as the fulcrum is incorrect because the goal is to
move the boat, not the oarlock. Ideally the oar shouldn't move in the water at
all, but in reality it actually moves forward somewhat over the course of the
stroke. This actually creates a small pocket of water vapor in front of the
blade which is a form of cavitation; if this weren't the case then the blade
would be very difficult to feather.

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jgrahamc
I disagree.

An oar is a first degree/class lever because the rowlock is not at the end of
the oar, but somewhere between my hand and the blade. But perhaps we learnt
different definitions of first/second class levers.

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Alex3917
I found this by searching for fulcrum on rec.sport.rowing:

"where the fulcrum lies depends on your point of view. If your POV is moving
along with the boat (say looking down on the pin) then the fulcrum is indeed
at the pin. If your POV is stationary with the water, then the fulcrum would
be at the point which you describe (on the loom of the oar, right before the
blade). It's all relative, and the forces and equations will work out, if you
stay consistant, no matter where you assign the 'fulcrum' to be."

I still actually think the NYTimes description is very misleading though. The
length of the stroke the rower takes in the boat is the same regardless of how
long the distance between the pin and the hands is, which means you aren't
moving the boat as much with a longer inboard. So the reason it feels easier
isn't because you're doing the same amount of work with a longer lever, it's
because you're doing less work.

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t0pj
One theme taken from the article is that, for the most part, practice came
before theory. Only later were likely (and even unlikely) explanations given
for the practice.

I think the turning point between practice/theory could've actually happened
within the 20th; black holes were thought to exist using available data and
were then later discovered.

