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Re: Re: Re: Re: "slight change at initiation" and proof


Posted by: JJA (jjanagnost@att.net) on Sat May 28 22:29:36 2005


> >>> Proving your “assertion” should not just be for my benefit alone. Forget me, - do it for your readers’ sake. Or do you feel that you can just make any statement you want about batting a baseball and expect everyone to believe? Or is it that you don’t want to offer supporting proof, because you can’t?
>
> Your quote:
> >>>In the past, you have not even accepted the fact that the application of torque at the handle is a factor in the bat’s trajectories.<<<
>
> That is either a lie or a very bad mistake by you. To make a statement like that about someone does demand proof. Prove it. <<<
>
> Hi Ray
>
> As I pointed out in the post “Hitting the outside pitch,” the changes in the bat’s trajectory for inside to outside pitches is mainly governed by the torque the batter applies during initiation. If you wish this discussion to continue, you will clarify your position on torque as a factor in generating bat-head acceleration.
>
> Therefore, I repeat the question -- Do you accept or reject what is stated at http://www.batspeed.com/research10.html ?
>
> No attempt to sidestep the question will be accepted.
>
> Jack Mankin

Strictly speaking, the definition of torque given in research10.html is not correct. It does not require forces in opposite direction for a body to rotate. For example, in your upper picture, you show two forces in the same direction and a "reaction". In that picture, you correctly note that the body does not rotate.

However, this is because the forces are applied at equal distances from the center of mass of the rectangle. This is why the body does not rotate. If you had used only one of the two force lines, say the top one but not the bottom one, the rectangle would initially rotate in a clockwise fashion. This is due to the torque that results from the upper force times the lever arm from the applied force to the center of mass of the object.

This is why the definition of torque in physics books is more precise than the layman's version in your definition. Here's a typical definition:

The torque on an object about some pivot point is the vector cross product of the lever arm with the applied force.

-JJA


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