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When Cecil Fielder hits a ball with his best swing the ball leaves the bat 1 degree hotter than when it left the pitcher?s hand (Knobler 2). An average head wind of 10 miles per hour can turn a 400-foot homer to a 370-foot fly ball out (Adair Cover). A batted ball can?t travel more than 545 feet (Adair Cover). All of these interesting facts can be proven by physics principles. Some of these principles aren?t so simple; some of them are quite simple. Physics effects many aspects of baseball; the most influenced being the art of pitching. The three pitches most affected by physics are the curve ball, knuckle ball, and the fastball.
Professor Robert Romer, editor of the American Journal of Physics, once said, ?There are two unsolved problems which interest me deeply. The first is the unified field theory [which explains the basic structure and formation of the universe]; the second is why does a baseball curve? I believe that, in my lifetime, we may solve the first, but I despair of the second.? (Adair 22) While there is much controversy as to why the baseball curves; there is no doubt that much science is involved. The physiology of the wrist and hand make the spin for a right-hander and a southpaw different. The natural rotation of the wrist of a right-handed pitcher makes the ball spin clockwise, making the ball break into the left-handed batter and away from the right-handed batter. The converse is true for a left-handed pitcher. If a different break is wanted the pitcher must rotate the wrist against nature. The screwball is a result, but so are elbow problems (Brancazio 2). Not only does anatomy affect the curve of a baseball. There are many influences of physics on the movement of a ball. There are two theories on which the curve of a curve ball is based. They are the Bernoulli Principle and the Magnus Effect.
The Magnus Effect is the more popular view of why the curve ball curves. The Magnus Effect comes with some controversy, however. The originator?s name is even in question. Some sources quote his name as Gustav Magnus (Brancazio 1, Knobler 2) while some quote his name as Heinrich Magnus (The Physics of Sport Lecture 6). It also isn?t clear what Mr. Magnus was trying to find out when he discovered the Magnus Effect. One theory is that he was trying to figure out the ?deflection of rotating artillery shells for the Prussian Artillery Commission (The Physics of Sport Lecture 6).? While the origin of the Magnus Effect isn?t clear the meaning of the Effect is crystal. According to Robert K. Adair, the ?Physicist of the National League,? the Magnus Force is ?a force directed at right angles to the direction of the air velocity and to the axis of spin (Adair 12).? If the ball spins counterclockwise with the ball velocity going directly forward, the sideways or Magnus force will be to the right as well (see figure 1).
Consider that a curve ball is thrown by a right-handed pitcher at a speed of 70 mph so that it rotates 17 times counterclockwise in its trip of about 60 feet from the pitcher?s hand to the plate; such a ball will be rotating at a of about 1800 rpm; i.e., about one-half the rate of a typical small synchronous electric motor. The side of the ball toward third base then travels about 15 times 9?(the circumference of the ball), equal to 11?, further than 60?, while the side toward first base travels 11? less than 60?. The velocity of the third-base side is about 82 mph, and the velocity of the first-base side is only 58 mph. ? The drag force increases with velocity i.e., the difference in the pressure of the air on the front face of the moving ball is greater than on the rear face, and that pressure difference increases with velocity. We can then expect the air pressure on the third-base side of the ball, which is traveling faster through the air, to be greater than the pressure on the first-base side, which is traveling more slowly, and the ball will be deflected toward first base (Adair 13).
If a ball is spinning slower on one side it will break toward that side. The formula for calculating force of the Magnus Force is MF=KwVCv where MF is the Magnus Force, K is the Magnus Coefficient, w is the Spin frequency (rpm), V is the velocity of the ball (mph), and Cv is the drag coefficient (Adair 22). For a ball traveling 70 mph, the drag coefficient (Cv) is approximately .5 (Adair 8) and the average spin frequency (w) of a major league curve ball is 1600 rpm (Knobler 2) and the Magnus coefficient (K) is 2.00 x 10-6 (Adair 22). These measurements calculate out to make the Magnus force (MF) equal .112 pounds force. This measurement provides us with the actual movement known as the ?sagitta?the largest deviation from the straight line?, and it only reaches 3.4? (Adair 30). Despite only moving 3, inches the batter sees that the ball breaks about 14? from the inside corner to the outside corner (Adair 29). This is why a good curve can buckle a batter?s knees.
The Bernoulli Principle states ?the faster an air stream is moving the lower the pressure in that air stream (Why Does 1).? The ball spins when it leaves the pitcher?s hand (except on a knuckle ball). While spinning the air next to the surface of the ball goes with it; if the ball is spinning fast enough the air is moving faster on one side than the other, creating uneven pressure on the sides of the ball. The slower moving air pushes the ball to one side creating the break of the pitch (Why Does 1).
The knuckle ball is the hardest ball to catch, which would also make it the hardest ball to hit. A properly thrown knuckle ball has about 25 rpm, compared to 1800 rpm for the average fastball. It makes less than one rotation in its trip to the plate, whereas the fastball makes about 10 (Kleinbaum 4). The movement is induced by the turbulence created by the stitches on the ball (Adair 31). ?A knuckleball, however, leaves the pitcher?s hand with virtually no spin. So, the motion caused by the asymmetry of the stitches causes the ball to move. But once the ball moves, its stitches are in a slightly different orientation relative to the flow of the air, so the ball will move again, in a different direction (Kleinbaum 4).? The movement of the curve ball is in continuous motion from either left to right or visa versa, whereas the motion of the knuckle ball is constantly changing until it reaches the catcher. A well-thrown knuckler is said to dance as it approaches the plate, moving from left to right and maybe back to the left. An effect that adds to the movement of the knuckle ball is the wake produced behind the ball. When there is little wake, as in a fastball, there is little movement. The knuckle ball has a large amount of wake and the wake field can fluctuate in size and in place, adding to the erratic flight of the ball (K-ball 2). When the speed of a non-rotating ball increases (this pitch is called a splitfinger fastball or a forkball, but is more like a fast knuckleball) the movement of the ball becomes more violent. When it reaches the end of its path it will drop quickly creating an almost unhittable ball (K-ball 3). These two theories explain the unpredictable movement of the knuckleball. As Robert Adair puts it, ?Most knuckleballs just go one way or the other, but nobody knows which way they?re going to go (Knobler 3).? Leaving the batter, pitcher, and most of all, the catcher at the mercy of the laws of physics.
The fastball is the most often used pitch in the game of baseball, and is also the most diverse pitch used. With names varying from rising fastball to sinkerball to cut fastball, it is the definitely the most versatile pitch in the game. A fastball can be used in any situation, it is also the pitch used when a pitcher wants to ?show his stuff.? The best fastballs in the major leagues are the ones that have movement, and the best movement is what Joe Morgan calls ?late movement.? One type of ?late movement? is the rising fastball. There are many myths surrounding the rising fastball that physics easily disprove. The myth is that with enough backspin a Magnus Force affects the ball, creating a last second jump of the ball; however, it is merely an illusion (Brancazio 3). According to ballplayers the ball rises slightly at the end of the pitch, but baseballs do not ?hop.?
?the 90-mph fast ball must fall almost 3 feet on its way to the plate if there is no hop, the effect of the back spin must be such as to ?curve? the ball upward about 3 feet if the ball is to rise. But the magnitude of that hop will be duplicated by a pitcher who throws a 90-mph fast ball sidearm, with a sidespin instead of backspin, ? But who has seen a fast ball curve 3 feet? In fact a hard fast ball thrown sidearm (or with a three-quarter motion) will tail no more than 6 inches, if that much. Therefore overhand fast balls certainly do not rise, ?(Adair 37)
A player?s perspective has much to do with the path of the ball, for example when a player watches from the dugout or the on deck circle (see figure 2) the ball will drop the three feet required by gravity. While the batter in the batters box will think it is in a straight line or that it may even rise 5-6 inches (Adair 39). A split finger fastball will actually drop at the end of its path to the plate. A cut fastball will actually break right or left, depending on the pitcher throwing hand. Along with the movement that makes a good fastball, a pitcher can change speeds just a little bit and get batters swinging from their heels.
The knuckleball, fastball, and most of all the curveball are the hardest pitches to hit in today?s game. Whether it is Tim Wakefield (ironic isn?t it) pitching a knuckleball, Pedro Martinez pitching his curveball, or Randy Johnson pitching his cut fastball, the batters and pitchers are controlled by Physics principles. The Magnus Effect, Bernoulli Principle, and the turbulence created by spin or the lack thereof are very evident in the pitching of today.
Works Cited
Adair, Robert K. The Physics of Baseball. New York: HarperCollins Publishers, Inc., 1994.
Brancazio, Professor Peter J. ?The Mechanics of a Breaking Pitch, The Physics of a Curveball.? Popular Mechanics April 1997. 29 Nov. 1999 Available http://popularmechanics.com/popmech/sci/9704STSSAM.html
Conley, Ken, Chang Choi and Joe Giuliani. ?The Physics of Baseball; The Curveball; I. Why Does a Curveball Curve?? October 1997. Online. Internet. 20 Nov 1999. Available http://library.advanced.org/11902/physics/curve1.html
Conley, Ken, Chang Choi and Joe Giuliani. ?The Physics of Baseball; The Curveball; II. Why Does a Curveball Curve? ? The Physics Principles.? 1997. Online. Internet. 20 Nov 1999. Available http://library.advanced.org/11902/physics/curve2.html
?K-ball Physics Explained.? On-line. Internet. 10 Nov. 1999. 20 Dec. 1999.
http://oddball-mall.com/knuckleball/mego.htm
Knobler, Mike. ?Hard Breaking Balls Haven?t Thrown This Physicist for a Curve.? The Jackson (MS) Clarion-Ledger 10 June 1997. 15 Dec. 1999. Available http://www2.netdoor.com/~crogers/knobler.html
Norcross, Tracy, Robbie Scruggs, Jenny Taylor, and Eric Thomen. ?What Makes a Curveball?? On-line. Internet. 15 December 1999. Available http://bridgewater.edu/~rbowman/phys105/p7/curveballs.html
Kleinbaum, Adam. ?The Physics of Baseball.? On-line. Internet. 04 May 1997. 20 Dec. 1999. http://www.hcs.harvard.edu/~hsr/hsr/winter97/bball.html
?The Physics of Baseball? 22 Sept. 1999. 15 Dec. 1999 On-line. Internet. Available http://users.javanet.com/~bkrudy/physics.html
?The Physics of Baseball 101.? 02 July 1999. 15 Dec. 1999 On-line. Internet. Available http://www.coloradorockies.com/rockies/101/physics.html
?Physics of Sports Lecture 17: Aerodynamics and Lift? On-line. Internet. 12 May 1999. 15 Nov. 1999. Available http://courses.washington.edu/phys208/notes/lect17.html
?Why does a Curve ball Curve?? Lansing State Journal 14 April 1993. 15 December 1999 Available http://www.pa.msu.edu/~sciencet/ask_st/041493.html
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