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Old 07-08-2011, 02:36 PM   #27
julian
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Join Date: Dec 2006
Location: Bedford,Massachusetts,US
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Default Two parts of an equation

Quote:
Originally Posted by kaiser View Post
So the pendulum action you are referring to is a rotation of the wrist around the axis going through the forarm, and not around the axis perpendicular to that going through the wrist (i.e. from thumb to little finger)?

Because if the latter, the pendulum action would be in the plane of the swing path which is mostly in the horizontal plane, and more so when the player meets the ball higher in the bounce. This means gravity, and hence g, would only play a small role in the pendulum action and g would need to be replaced by a, the accelleration of the racket arm executed by the player.

If the pendulum action you're referring to is a rotation around the forearm axis, as in the modern 'windscreen-wiper' stroke, it would be perpendicular to the plane of the swing path and therefore mostly in the vertical plane. Then gravity does play a role, but not exclusively. When you rotate your forearm to bring the rackethead up during the take-back, you store energy in the forearm by twisting the radius and ulna bones relative to each other. When you then bring arm foreward during the stroke, the radius and ulna are forced back into their original position, releasing this stored energy into a rotation of the wrist and, hence, the racket. This rotational force therefore also affects the pendulum action around the wrist, as well as gravity, creating an angular accelleration on top of g.

Shouldn't this also be accounted for in your formula? How would this affect your conclusions?
1.An observation by OP ( call it a 21 formula) can make sense
2.A justification to the best of my knowledge has a lot of weak points
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