The direction of baseballs after they are thrown is caused by the spin of the ball. Spin is defined as rotations around the axis of the baseball. Major league pitchers have timed the spin on their pitches at 1,500 rpm. So when a baseball spins in the air, the wires in the ball cause a self-created "air pocket" that causes changes in direction. This is called the Magnus effect. The rotation of a baseball is defined as a vector that points to the rotation of the axis. And the magnitude of this rotation vector is the number of revolutions per second, this is called an angular velocity vector (Horney, A., Lowry, T., Schwenker, E. and Wray, E. (2008). A New Version of Baseball. Electronic Proceedings of Undergraduate Mathematics, 3 (4)). All baseballs are affected by this spin and it is the spin that causes the change in direction. When fastballs are thrown, the spin of the ball affects the ball and causes it to travel through the air at a higher speed. This also increases the air mass under the ball and makes the air above the ball thinner. This creates lift and is what makes the ball faster and causes more velocity. A curveball is almost the exact opposite of a fastball. While a fastball spins and flies the pitch straight, a curveball spins in the opposite direction. Downward rotation makes the air around the terrain heavy at the top and lighter at the bottom; this causes the ball to fall or break. According to Mlb.com's game day app, a typical major league curveball averages less than 80 mph. While the average fastball pitch is over 87 mph. The following data comes from curveballs from Bronson Arroyo of the Cincinnati Reds and fastballs from Josh Beckett of the Boston Red Socks. Although the nature of the movement on a curveball is middle of paper......of the ball. Lift is only important for ball spin if it is a fastball, because the ball creates its own ball. In the 1920s, pitchers used several ways to cheat by adding friction to balls illegally. Pitchers sometimes used pine tar, tobacco juice, or mud on baseballs, which affected the grip and friction of the ball. This caused the balls to be affected even more by the spin of the baseball. Pitchers also used lotion or filed the ball to make it smoother so that base balls could travel through the air faster. This was banned because it could make the pitches wild and put the batter in danger. Works Cited (http://www.grc.nasa.gov/WWW/k-12/airplane/ballforce.html Horney, A., Lowry, T., Schwenker, E. and Wray, E. (2008). new version of baseball Electronic Proceedings of Undergraduate Mathematics.., 3(4)).