Physics of Baseball

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Baseball is a fascinating sport that is exceptionally fun to play. This assignment is all about understanding the physics of a few key aspects of this sport. One might ask what physics could have to do with baseball? Like most sports baseball involves physical motion. Baseball encompasses all three planes of motion through throwing, hitting, and fielding. All of the classical laws of mechanics can be applied to understand the physics of this game.

Baseball is not a difficult game to comprehend, but it can a very long time to achieve a high level of performance. Usually one starts playing this game at a very young age and the first thing they start out with is throwing. Throwing a baseball involves exploiting all major muscle groups in the body to generate a large torque on the arm that will in turn create a high potential for speed when it is released.


Throwing is a fairly natural activity for a person. Everyone at some point in time has thrown some object at a person. In baseball throwing becomes an art. Throwing a baseball is a relatively easy task, but throwing it accurately and with a high speed is difficult. People who play this sport spend a very long time perfecting their throw.

When one throws a baseball properly they are using there entire body to generate a large force to propel the baseball. A general throwing position starts with a person rotated 90 degrees from there target with there throwing arm 180 degrees from the target and parallel to the ground. The person then starts rotating their body back towards their target while there throwing arm starts bending until it is almost 90 degrees to their elbow, while the arm is bending at the elbow the throwing arm is rotating such that the arm rotates back almost 180 degrees from the target. Meanwhile the person is leaping forward with the leg that was initially pointed at the target while there other leg is planted into the ground. The person is bending at their waist and the other arm is rotating into their body. Around the point where the driving leg strikes the ground the throwing arm is rotating foreword at a tremendous angular speed and the person lets go of the ball. At the point where the ball is let go the persons body pulls the planted leg forward and the throwing arm finishes its motion towards the driving leg.

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"Physics of Baseball." 26 Mar 2017

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The person is then generally square with the target.

From this one can determine that it isn’t exactly easy to throw a ball properly. To be honest, it takes a lot of talent and hard work to achieve the perfection that major league players have. It is interesting to know that most major league pitchers arms are rotating around 90 to 100 mph during the firing stage.
So what just exactly is this torque coming from? It is coming from all of the forces in your body working together and acting on your arm. Even though most of the component forces come from many different parts of the body, they are all linked together in such a way they generate a large resultant force that pulls the arm back and then it rotates it foreword. It is helpful to visualize this like a whip. During the loading phase you are using your body to move the tip of the whip behind you and when you fire it the tip rotates forward at an extremely fast angular speed. The process of throwing acts very much the same way. During the loading phase of throwing your body is rotating your arm backwards using the combined forces from your body until the point where your arm stops rotating backwards and it starts rotating foreword at a very high speed from the torque. Part of the torque that rotates the arm forward comes from your arms resistance to rotating backwards. Try putting your forearm 90 degrees to the rest of your arm that is parallel to the ground, then try rotating it backwards. You should notice that the farther you rotate your armback the faster your arm wants to spring back.

One of the most interesting things about baseball is the motion of an actual baseball as it travels its path. This motion can be fairly unpredictable at times.


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.

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.

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.

There is very little that can match the excitement one experiences when they hit a baseball flawlessly. This experience although exhilarating is very difficult to do. In the major leagues the ball takes less than a half a second for the ball to cross the plate once the pitcher has released the ball. Given that it takes a quarter of a second to complete a swing, a tenth of a second do decide where to swing, and the time for the ball to cross the plate is about a hundredth of a second. The actual collision lasts for about a thousandth of a second. This happens incredibly fast. In fact, hitting a 90 mph fastball is considered hardest thing to do in any sport according to many experts. "If a person from another planet was told what's involved ... they would say it's impossible," says Porter Johnson, a physics professor at Illinois Institute of Technology in Chicago. [1]

Hitting the baseball perfectly is often called hitting the sweet spot. This location varies on all bats, but it is generally considered to be about 5 to 7 inches from the end of the barrel. When you hit an object with a wood bat at the sweet spot you are hitting the fundamental node. When the bat meets the baseball the collision causes the bat vibrate. Hitting a baseball on the wrong part of the bat can be painful, especially on a cold day. If you hit the ball at the fundamental mode the bat doesn’t vibrate. In physics the collision of the bat and the ball is considered elastic. An elastic collision between two objects is one in which the total kinetic energy and total momentum is the same before and after the collision. When you swing a bat you are doing work. If the collision causes the bat to vibrate it is doing work and hence it is using energy. Since the energy is conserved, the energy from the collision must equal the energy of the system after the collision. The collision causes the bat to vibrate hence there is less energy that can be transferred to the ball because energy from the collision was used in the vibrations.

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