The ball rotates as it travels through the air, due to the seams. There is air resistance caused by the seams. "As the ball is traveling through the air it is creating high and low pressure fronts." (Motion of a Ball)
The grip determines the rotation of the ball.
"Top view of clockwise spinning baseball moving from the bottom of the page to the top of the page:
a) interpretation using Newton's Third Law; b) explanation involving a boundary layer."
The Magnus Force
" A rotating sphere moving through air drags a boundary layer of air along with its surface. The air molecules that encounter this boundary layer get dragged along to some extent. This causes the air molecules on the right side of the ball in Figure b to be accelerated and those on the left side to be slowed down. The differentially higher speed of air on the right side implies a lower pressure due to the Bernoulli Effect and thus causes a deflection to the right. This is known as the Magnus effect." (Bauer, Westfall, pg. 349)
Rise Ball
Does a Rise Ball actually Rise??
The answer, no! It doesn't actually rise, but it falls slower than a fastball and doesn't have backspin. Because the rise ball travels on a more level plane, it doesn't have the same gravitational drop and batters perceive it to rise.
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