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Re: F=MA by Steve


Posted by: MissouriDad (zach3737@aol.com) on Sat Jan 8 23:38:56 2000


Steve or Jack,
Using conservation of momentum and taking into effect the coeficient or restitution you can come up with a balls exit velocity and the supposed velocity of the bat after contact. I think if you measured the bat speed right after contact you would see it hasn't slowed as much as pure conservation of momentum would suggest. This amount of "non-slowing" is due to external forces being applied to the bat (by the batter). If conservation of momentum says bat would be going 35 mph after contact and it is actually still going 55 mph we have force being applied mass x acceleration. The next thing you're gonna think is "ok the ball will be exiting at 167 mph rather than the 146 mph that conservation of momentum alone would suggest" wrong!!! First off I think a conservation of momentum equation where 29 oz is used for the bat is wrong (Steve was willing to say not all of the 33 oz is applied so he arbitrarily dropped it to 29 oz). I think the effective bat weight would be much less. To make a long story short I think conservation of momentum is the major player in ball exit velocity, but not quite as large a percentage as Steve would suggest. I think Force is another contributor, and the resistance that the batter applies by simply holding on to the bat will create a moment around the center of mass of the bat, this moment is also a contributor. (if a bat were traveling at 85 mph with no one holding the handle, when the ball hit aprroximately 5 inches away from the center of mass of the bat, the bat would be caused to rotate). The mere fact that it doesn't rotate is caused from a moment that is created by the hands which is AT LEAST equal and opposite to the moment caused by the ball. As I asked before, to really get into the meat of this discussion, does anyone have any actual bat velocities right after contact? That will be a start.

Please excuse any numbers that I used above. I used them out of memory and never intended for them to be totally accurate, I was just using them to demonstrate a point.


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