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Angular Momentum and Kuerten:
They say that connections appear everywhere and the great composers loved to go to Italy to study such things as Michaelangelos and Raphaels as that enabled them to understand the Beethoven. I like to go to tennis to study the market and a visit to the US Open yesterday was particularly instructive. I always watch the practice sessions and fortunately, Gustavo Kuerten, Brazil, best in world on clay was practicing on an accessible court. His practice opponent had a continuous motion on a spin serve with an arc like a circle from start to finish and a sharp acceleration at impact after a very low toss. The velocity he imparted was greater because of the speed from the continuous motion and the directness of the angular force he applied in a straight line with the body and the point in the opponent's corner he was aiming at. I tried the serve at home and found that from left to right I could finally reach a point on the second bounce almost as far away from me as my first serve, versus perhaps 80% without the continuous motion and Agassiz type toss..... I immediately thought that the concept of angular momentum mite be useful in the market. Let's take the last 10 changes in the SP for the last two weeks
|Week of 8/16||Week of 8/23|
The rank correlation between the weeks was about 0.90. The cross products were 134 out of a total possibility of 164 (obtained by summing up the absolute values of the cross products) for a total ratio of about 0.80. Thus the angular momentum from one week to the next was certainly not in the opposite direction. I hypothesize that in weeks with large changes in one direction the rank correlations and cross product correlations tend to be highly negative. In general I hypothesize that the rank correlations and cross product correlations will tend to have a non-random distribution. And to this end, I may write a few Liberty Basic statements to test. -- Victor Niederhoffer
A Reader Replies:
I challenge your statement that continuous motion leads to more powerful serves. I fully understand the reasoning behind this, simply that acceleration (racquet head speed) is more maintained if it is continuous. This is outdated conventional wisdom. Currently, the world's most powerful servers, Roddick, Rusedski, Dent, have 2 motions in their serves. 1 to bring the racquet into the "cocked" position (like a revolver pistol), and then a hitch and fire motion once the racquet is set in firing position. The result = the most powerful serves in history. Let me know if I can assist you in testing this.
Professor Charles Pennington Adds:
Yes, my little bits and pieces of physics are always oversimplifications of something like a tennis stroke--efforts to get some grasp or understanding of something that's very complicated.
The standard story of the theorist--
He gives a wonderful and convincing explanation of why a recent experiment was reported with result X.
But there was a mistake. The experimentalist made a typo, and the correct experimental result was NOT X.
The theorist says "I can explain that too!"
Despite all this, I like to try. Sometimes you really can get insight from simple principles-