How does a machine make the ball “curve”?
What makes a ball “curve” is the spin. If you throw an overhand fastball, the ball has backspin. If it were not for gravity, this ball would curve upward. Because gravity counteracts the effect of the spin and prevents it from curving upward, the ball appears to travel in a straight line. If you throw an overhand curve, the ball actually spins in the opposite direction. The spin goes forward, which causes the ball to curve downward. Since the ball is curving toward the ground, gravity does not prevent it from curving. It actually helps it. Our machines make the ball curve by putting different spins on the ball. On a BATA-2 this is done by setting one wheel to rotate faster than the other.
