Motion of a Baseball

Figure 4: Ball Trail

After you have managed to generate a large amount of torque in your throwing arm the ball will be released. What happens to the baseball? This is where physics can come in handy. When you throw a baseball there are several things that can have a large affect on the motion of a baseball as it is traveling, but a couple of the most important ones are grip and the release point. The reason the grip is so important is because the baseball has raised seams. When the ball is traveling through the air it is rotating. Since there is air resistance the seams play a key role in the motion of the baseball. Just like airplanes can maneuver through the air by means of a rudder and ailerons, the seams in conjunction with the rotation can cause the ball to move in a slightly comparable manor. As the ball is traveling through the air it is creating high and low pressure fronts. The seams can cause turbulence in the motion. Figure 5 shows a picture of the pressure fronts around a baseball.

Figure 5: Pressure fronts and flight path

The reason why grip has a lot to do with the motion of the baseball is it largely determines the rotation of the baseball. Take for an example a paper airplane. Try throwing it a few times while gripping it at different points on the paper airplane. You should notice a difference in the motion of each grip. Throwing a baseball with a different grip acts very much the same. The rotation of the baseball in combination with the way the seam is spinning through the air causes the ball to move in different patterns.  A few common pitches are the fastball, curve ball, slider, and the screwball. Each of these pitches has a different spin because of how the player grips the ball. Figure 6 shows a picture of what the spin looks like from the batters view of a right-handed pitcher.

Figure 6: Spin rotation of different pitches

Now comes the interesting part. Not only can most major league pitchers throw upwards in the 90 to 100 mph range, they can also throw pitches that move in wildly unpredictable patterns and change the magnitude of the velocity from pitch to pitch. This is makes hitting at a major league level very challenging. 


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