What causes a thrown baseball to curve?

[nst.john]

I'm an avid baseball fan and since I've gotten interested in physics, it's pretty cool to try to combine the two.

I was wondering what forces act on a thrown baseball and how the spin and the seams of the ball cause it to curve.

 

[dauto]

As the spinning ball moves through the air, the surface of the ball drags air molecules along with it causing the air pressure to be slightly larger on one side of the ball (and smaller on the opposite side) This pressure differential creates a sideways force on the ball curving its path. This is called Magnus effect.

 

[rcgldr]

The airflow near the surface of the ball remains "attached" longer on the side that is spinning backwards from the direction of travel, causing the air in the "wake" left behind the ball to get diverted a bit towards the side that is spinning forwards from the direction of travel. Wiki article:

http://en.wikipedia.org/wiki/Magnus_effect

 

[Chestermiller]

I'm an avid baseball fan and since I've gotten interested in physics, it's pretty cool to try to combine the two.

I was wondering what forces act on a thrown baseball and how the spin and the seams of the ball cause it to curve.

If you are interested in the physics of baseball, look up on Amazon the book entitled "The Physics of Baseball" that came out a few decades ago. It is still very popular, and gives good explanations.

Chet