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# Physics/backspin after contact with bat/distance

Question
Could you explain why more backspin [hitting ball under the CG] may, or may not, affect the absolute distance of a home run.

It seems to me that the MOST backspin is created by foul balls, therefore I don't really see why everyone thinks that MORE backspin can/will somewhere create LONGER home runs?????  My own anecdotal college hitting experience suggest that my longest home runs actually left the bat with VERY LITTLE SPIN, and were in fact more like knuckleballs -- and not sure what/how to impart this info. to my boys.

Thanks -- you seem to have a very good feel for the math on this, appreciate your help,

Craig

The principle idea behind this is what is known as the Magnus Effect. What happens is the backspin pulls air over and down behind the ball. Because of Newton's Third every action results in an equal but opposite reaction. The force downward on the air by the Magnus Effect generates an equal but opposite upward force on the ball. I suppose that in principle this upward force could increase the flight time and, therefore, the range of the ball.

Physics

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#### James J. Kovalcin

##### Expertise

I am teaching or have taught AP physics B and C [calculus based mechanics & electricity and magnetism] as well as Lab Physics for college bound students. I have a BS in Physics from the University of Pittsburgh and a Master of Arts in Teaching from same. I have been teaching physics for 34 years. I am constantly updating my skills and have a particular interest in modern physics topics.