SIMILIAR STUDY, DIFFERENT BALL: Kinesiologists at Purdue University used the principles of physics to explain why a fastball pitch in baseball is hard to hit and how a curveball gets its motion. A batter often underestimates how fast a ball is moving and whether it's a fastball or not. This causes the player to misjudge where the ball and bat will meet. After the pitch is thrown, the batter must predict where the ball will pass through the hitting area. If the player has underestimated the speed of the ball, he or she will swing too low, at the place where he or she thought the ball would be. The greater the difference between the estimate and the actual speed of the pitch, the greater this error becomes, making it harder to hit a fastball. To achieve a curveball, the pitcher spins the ball, causing the air to move faster on one side of the ball, creating a pressure difference. This causes the ball to push to one side and curve in that direction. Most pitchers spin the ball so that the downward motion of a curveball is much greater than any horizontal movement.