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09-05-2012, 03:06 AM   #173
stoneage
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Join Date: Apr 2010
Location: Stockholm, Sweden
Posts: 243

Quote:
 Originally Posted by corners Rod Cross has been modeling tennis strokes, including the serve, as double pendulums for several years, with two papers appearing in the past twelve months.
I have read his A double pendulum model of tennis strokes in American Association of Physics Teachers. I can find nothing there that even remotely support the use of MgR/I. He is studying a double pendulum with an applied force and without gravity (see fig 1 and the appendix) which have a very different behavior.
Any other sources?

Quote:
 This isn't the case. Many racquets on the market are reasonably close to 21.0, especially traditional players' frames like the Pro Staff 6.0 and the Prestiges. I support your skepticism but I think you're misinterpreting this notion of MgR/I and its use. It's not meant as a stand-alone, be all/end all. If the ratio doesn't make some sense to you after these experiments then we can confidently add your report to the "MgR/I is rubbish." pile of anecdotes.
Say you have two parameters A=10 and B=5

1. If you say that A=10 and B=5, then saying that A/B = 2 doesn't ad any information, it follows automatically.

2. If you say that B = 5 and A/B = 2, it is the same as in 1. just a slightly more complicated way of saying that A=10 and B=5

3. If you only say that A/B = 2 then you have solutions like A = 5 800 and B = 2 400

You admit that 3. is not sufficient and you have to set B as well. If you want to describe your relation as 2. fine, as long as you are aware that it is the same as 1.

So I don't doubt that your customization work. But it does so because you set the fundamental properties, not the relation.