Re: .Bernoulli and curve balls.

["Paul Camp" <pjcamp@coastal.edu>]

> Paul Camp says:
> > ....
> > In addition to that horizontal rotation is a backward rotation 
> > imparted when the ball rolls off the fingers so all told the top of 
> > the ball, as seen by a right-hander, is coming back and to the right. 
> > If you do this, the ball curves down and to the right 
> > which brings it low and inside to a left-handed batter. Low and 
> > inside is good. It is hard to hit to begin with and if the ball is 
> > hit, tends to hook foul.
> > ....
>
> Do I read this correctly to say that the baseball curves in the direction
> opposite to it's spin?
>
> -- 
> --James McLean

I'm not sure that means anything since the spin is round and round. 
The Magnus force is larger on the side with the greater speed 
relative to the air which *should* be down and to the right as seen 
by the pitcher. So you are right, I must have gotten the rotation 
sense wrong (very busy day) -- if I was thinking of fast balls at the 
same time that would make sense as a curve ball rotates in the 
opposite sense from a fast ball. Anyway, what *really* happens (and 
what makes them hard to throw): The pitcher attempts to make the ball 
rotate opposite to the way it would normally roll off the fingers 
which means giving a sharp downward snap to the front of the ball. 
Adding the wrist motion makes it actually rotate at an angle rather 
than exactly opposite to the rotation of the fastball and this is 
what brings it inside on a leftie as well as going down. A good curve 
can drop as much as 2 feet beyond what a fastball would do.

Sorry for the mixup.

Paul J. Camp                   "The Beauty of the Universe
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