Science at Work in Baseball (Benchmark Rockets)

Hantula

Science at Work in

BASEBALL Why does a curveball curve? Why does a base stealer slide into second? Why is a day-game home run sometimes a nightgame long out? A few basic ideas in science can answer these questions and explain why many other things happen the way they do on a baseball field.

TITLES IN THIS SERIES: Science at Work in AUTO RACING Science at Work in BASEBALL Science at Work in BASKETBALL

Science at Work in FOOTBALL Science at Work in SNOWBOARDING Science at Work in SOCCER

Science at Work in BASEBALL

A batter trying to hit a home run, a striker trying to score a goal, a quarterback trying to throw a touchdown pass—what do these people have in common? They all depend on science to help them succeed. The laws of science are at work every time hitters step to the plate or quarterbacks step back to throw. Understanding these laws can help you enjoy watching and playing your favorite sport.

Bottom Bott Bo ttom tt om of of the the Nin inth thh

Science at Work in

BASEBALL By Richard Hantula Science and Curriculum Consultant: Debra Voege, M.A., Science Curriculum Resource Teacher

Science at Work in Baseball

Copyright © 2012 Marshall Cavendish Corporation Published by Marshall Cavendish Benchmark An imprint of Marshall Cavendish Corporation All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior permission of the copyright owner. Request for permission should be addressed to the Publisher, Marshall Cavendish Corporation, 99 White Plains Road, Tarrytown, NY 10591. Tel: (914) 332-8888, fax: (914) 332-1888. Website: www.marshallcavendish.us This publication represents the opinions and views of the author based on the author’s personal experience, knowledge, and research. The information in this book serves as a general guide only. The author and publisher have used their best efforts in preparing this book and disclaim liability rising directly and indirectly from the use and application of this book. Other Marshall Cavendish Offices: Marshall Cavendish International (Asia) Private Limited, 1 New Industrial Road, Singapore 536196 • Marshall Cavendish International (Thailand) Co Ltd. 253 Asoke, 12th Flr, Sukhumvit 21 Road, Klongtoey Nua, Wattana, Bangkok 10110, Thailand • Marshall Cavendish (Malaysia) Sdn Bhd, Times Subang, Lot 46, Subang Hi-Tech Industrial Park, Batu Tiga, 40000 Shah Alam, Selangor Darul Ehsan, Malaysia Marshall Cavendish is a trademark of Times Publishing Limited All websites were available and accurate when this book was sent to press. Library of Congress Cataloging-in-Publication Data Hantula, Richard. Science at work in baseball / Richard Hantula. p. cm. — (Sports science) Includes index. Summary: “Explains how the laws of science, especially physics, are at work in the game of baseball”—Provided by publisher. ISBN 978-1-60870-587-0 (print)—ISBN 978-1-60870-732-4 (ebook) 1. Baseball—Juvenile literature. 2. Physics—Juvenile literature. I. Title. II. Series. GV867.5.H36 2012 796.357—dc22 2010052886 Developed for Marshall Cavendish Benchmark by RJF Publishing LLC (www.RJFpublishing.com) Design: Westgraphix LLC/Tammy West Photo Research: Edward A. Thomas Cover: Shortstop Derek Jeter leaps over the sliding runner to make a quick throw to first for a double play. The photographs in this book are used by permission and through the courtesy of: Front Cover: Mike Ehrmann/WireImage/Getty Images. AP Images: Kathy Willens, 4; Mark Duncan, 5; Tony Gutierrez, 6; Winslow Townson, 22; Steve Nesius, 24; Ross D. Franklin, 29. Getty Images: NY Daily News Archive, 12; Otto Greule Jr./Stringer, 15; Elsa/Staff, 28. Newscom: Jim Cowsert/Icon SMI, 17; UPI/Lori Shepler, 18. Printed in Malaysia (T) 135642

CONTENTS

Chapter One Bottom of the Ninth . . . . . . 4

Chapter Two Hit That Ball! . . . . . . . . . . 12

Chapter Three Choosing Pitches . . . . . . . 18

Chapter Four In the Field . . . . . . . . . . . . 24 Glossary . . . . . . . . . . . . . . 30 Find Out More . . . . . . . . . 31 Index . . . . . . . . . . . . . . . . 32

Words defined in the glossary are in bold type the first time they appear in the text.

Science at Work in Baseball

CHAPTER

ONE

Bottom of the Ninth

Big-league pitchers throw so hard that a pitch may take less than half a second to reach home plate. Shown here: Tim Lincecum is about to throw. 4

Bottom of the Ninth

I

t’s the bottom of the ninth inning. There are two outs and no one on base. The team at bat is down by a run. The count on the batter is three balls and two strikes. It’s time to do or die. The pitcher will try to throw a strike. Giving up a walk would put the tying run on base. The batter wants to avoid striking out and ending the game. The batter will try to make good contact with the ball in hopes of getting on base or even knocking the ball out of the park for a home run. This situation is typical in a baseball game. To do their jobs, pitchers are trying to throw to precise spots and batters are trying to hit the ball just right. Both of these things can be very hard to do.

A Small Target The pitcher wants to throw the ball in the strike zone. This is an imaginary rectangle above home plate. It is For a pitch to be a strike, it must go over home plate between the batter’s knees and chest. Shown here: Miguel Cabrera waits for a pitch. 5

Science at Work in Baseball

How Fast Was That Fastball? The speed of pitched balls is measured with a radar gun. Baseball radar guns are not very different from the radar guns that police use to catch speeders on the highway. The radar gun sends out a beam of radio waves at a moving object—a ball or a car. Some of the waves bounce off the object

and go back to the radar gun. The object’s motion makes the returning waves slightly different from the ones the radar gun sent out. When the radar gun receives the return waves, it measures that difference and uses this information to calculate the object’s speed.

This radar gun behind home plate shows the speed of each pitch.

just 17 inches (43 centimeters) wide. In height it extends roughly from the batter’s knees to the batter’s chest. The strike zone is a small target. But some big-league pitchers can hit this target while throwing the ball as fast as 90 to 100 miles (145-160 kilometers) per hour. 6

Bottom of the Ninth

Pitchers also don’t want to throw a strike that is easy for the batter to hit. They often try to throw pitches that are around the edges of the strike zone.

Hitting Is Hard to Do The batter wants to hit the speeding ball. But a couple of things make this hard to do well. First, the pitcher is not very far away. In professional baseball, the pitcher starts the pitch just 60 feet 6 inches (18.4 meters) from the batter. This means a pitch can reach the batter in less than half a second! That is all the time the batter has to react and hit the ball. In that tiny amount of time the batter has to figure out the ball’s path, decide whether to swing or take the pitch, and (if swinging) get the bat around in order to make contact with the ball.

Batting Helmets A pitched ball speeding toward a batter has a lot of energy. This energy of motion is called kinetic energy. If the batter’s head gets in the way of the ball, the ball may suddenly stop, but its kinetic energy does not just disappear. Energy cannot be destroyed. Much of the ball’s energy goes to apply a very strong force to the batter’s head. This is why batters need to wear helmets. The helmet can safely absorb a lot of the ball’s kinetic energy and reduce

the chances that the batter will be injured. Even with a helmet on, though, it’s still possible to get a head injury if a baseball hits you in the head. Signs of a head injury can include pain, dizziness, vision problems, or unusual behavior. A player who has been hit in the head should never ignore such symptoms. He or she should be checked by a doctor and follow the doctor’s advice. If a head injury is not properly treated, the results can be very serious.

7

Science at Work in Baseball

A second thing also makes hitting hard to do. The bat and the ball are both round. Their shapes make it harder for a batter to make solid contact with the ball. If the batter doesn’t make contact squarely, the ball may go off in a direction the batter doesn’t want. It may be popped up or hit on the ground to an infielder. It may also be hit softly. In all of these situations, the batter is likely to be out.

PHYSICS FACT

Rules for Motion

Once the ball is in motion, First Law of Motion players have very little time If an object is at rest, it will stay to think about what they at rest unless a force acts on it. need to do. Good players If an object is moving, it will keep rely on the skills and instincts on moving in the same direction they’ve picked up through and at the same speed unless practice. Science, however, a force acts on it. can help them understand what they practice. There is a branch of science that deals with how objects move and what happens when one object hits another. That branch is called physics. People who study it are known as physicists. Physics can seem complicated. But ordinary objects in the everyday world, such as a bat and a ball, obey a few simple rules. In the 1600s, the English scientist Isaac Newton figured out a few key rules for the motion of objects. These rules are now called Newton’s laws of motion, or simply the laws of motion. They deal with the ways in which a force—anything that produces a push or a pull—affects an object. 8

Bottom of the Ninth

Major League Baseball Field Left Field

Foul Line

Center Field

Right Field

Second Base

Foul Line

90' Pitcher’s Mound Third Base

First Base 60' 6"

Home Plate

In Major League Baseball, the distance from the pitcher’s mound to home plate is just 60 feet, 6 inches. The distance between bases is 90 feet.

First Law of Motion The first of Newton’s laws has two parts. One part says that if an object is at rest—that is, not moving—it will stay that way unless some force causes it to move. The other part of Newton’s first law deals with a moving object. It says that the object will keep on moving at the same speed and in the same direction unless a force acts on it. 9

Science at Work in Baseball

When a pitcher throws a ball, that’s the first law of motion at work. The ball starts at rest in the pitcher’s hand. It is not going anywhere. The pitcher puts it in motion by throwing it toward home plate. The law’s second part says that once the ball is pitched, it will keep on traveling forever without changing its speed or its direction. However, it will do this only if no force acts on it. In real life, several different forces may affect it. Suppose the batter hits the ball. The bat applies a force that makes the ball go in a different direction. Most likely, the ball’s speed is changed as well. Suppose the ball goes past the batter and is caught by PHYSICS FACT the catcher. The catcher’s mitt Energy offers resistance to the ball’s Energy comes in different movement. This resistance is a forms. Heat is a form of force that stops the ball. If the energy. So is light. Kinetic ball happens to go past both energy is another example the batter and the catcher, the of a form of energy There’s backstop behind home plate will an important rule of supply the resistance to stop it. physics called the law of The law’s second part can be conservation of energy: said in a simpler way with the Energy cannot be destroyed. It can, however, be changed help of a special physics word: from one form to another. velocity. People sometimes use the word velocity to mean “speed.” But in physics, velocity means both the speed and the direction of an object. A physicist would simply say that an object will keep on moving at the same velocity unless a force acts on it. 10

Bottom of the Ninth

Natural Born Forces Actually, a ball thrown by a pitcher will sooner or later come to a stop even if there is no batter, no catcher, and no backstop. Even if a pitcher stands in an empty field, a pitched ball won’t keep on going forever. Natural forces bring it to a stop. One of these natural forces is Earth’s gravity. Gravity pulls downward on everything at or near Earth’s surface. Because of gravity, a thrown object, unless it is caught, will sooner or later fall to the ground. The air produces another important natural force. It offers resistance to anything that moves through it. This resistance is known as drag. For an object moving at a slow speed, the drag is very small. For objects moving at higher speeds, though, the drag can become quite large. You feel drag when you stick your hand out the window of a fast-moving car. When a baseball is hit or thrown, drag immediately starts working to slow down the ball.

Air versus No Air What if there were no air resistance? If Earth didn’t have any air, then the only force to stop a batted ball from traveling forever would be gravity. Without air, the ball would travel farther before being pulled to the ground by gravity. Just how much farther depends on the ball’s speed and on the direction in which it leaves the bat. A ball that is popped straight up will fall close to the batter. In

that case the air doesn’t make too much of a difference. But suppose that the ball’s path as it leaves the bat makes an angle of 45 degrees to the ground—that is, halfway between straight up and straight ahead. And suppose that the ball starts out traveling at a speed of 100 miles (160 kilometers) per hour. Then the ball would go about twice as far if there were no air. 11

CHAPTER

TWO

Hit That Ball!

Babe Ruth was one of the best home run hitters ever. He used a heavier bat than most players use today.

12

Hit That Ball!

I

t’s two out in the bottom of the ninth, and the team at bat is behind. The team’s manager has a lot to think about. How likely is it that the next scheduled batter will get a hit? Is it time to use a pinch hitter? Different batters hit the ball differently. The type of bat a hitter uses also makes a difference. In the end, it all boils down to physics.

Changing the Ball’s Velocity Whoever goes to the batter’s box must first apply force to the bat to put it into motion. The batter’s swing gives the bat velocity. If the bat hits the ball, the contact applies a force to the ball. This force makes the ball go in a new direction. Generally, the batter tries to hit the ball so that it stays within the foul lines and is a fair ball. Of course, this doesn’t always happen. But whatever direction the ball ends up going in, its velocity has been changed. The change in velocity usually also involves a change in speed. Physicists have a special name for a change in velocity. They call it acceleration. Many people use the word acceleration to mean “speeding up.” In physics, the word can mean that, but it can also refer to other changes in an object’s velocity. For a physicist, acceleration can mean a change in the direction of motion, an increase or decrease in speed, or both. An increase in speed is called a positive acceleration, and a decrease in speed a negative acceleration.

Second Law of Motion If the batter hits the ball hard enough, the ball may get enough acceleration for a home run. Force and acceleration obey a rule known as Newton’s second law of motion. 13

Science at Work in Baseball

The second law says that the acceleration received by an object depends on the force applied. The bigger the force, the greater the acceleration. So the harder the bat hits the ball, the faster the ball will go. An object’s mass is also important in Newton’s second law. Mass is the amount of matter the object contains. The second law says that the bigger the mass, the smaller the acceleration. Therefore, if the same force is applied to objects of different masses, the object with the bigger mass will have the smaller acceleration. Imagine an iron ball the size of a baseball. It has more mass than a baseball. If both balls are hit with a bat using the same amount of force, the iron ball will receive less acceleration than the baseball. In other words, heavier objects tend to resist acceleration more than lighter ones. An object’s PHYSICS FACT resistance to acceleration Second Law of Motion is called inertia. The more When a force acts on an object, the greater the force, the greater the mass an object has, the acceleration it gives to the object. If bigger its inertia. The more the same force is used on objects of inertia an object has, the different masses, objects with less bigger the force needed to mass receive more acceleration. accelerate the object to a certain speed.

Bat Meets Ball There’s another key physics idea that helps explain what happens when a bat hits a baseball. That idea is momentum. Momentum is a measure of an object’s motion. It depends on both the mass and the velocity of the 14

Hit That Ball!

object. The faster an object moves, the more momentum it has. Also, if different objects move at the same velocity, those with more mass have more momentum. Like energy, momentum is conserved. It does not disappear, but it can be transferred from one object to another. That is what happens when a batter swings and hits a ball. The moving bat has momentum. When the bat meets the ball, it transfers much of its momentum to the ball.

ICHIRO SUZUKI Seattle Mariners outfielder Ichiro Suzuki is one of the greatest hitters of all time. Storm chasers needinto Suzuki was born remember get back 1973 in to Japan, wherein he was a star player before coming to the United States. In 2001, his rookie season with the Mariners, he was med th me he Am Americ named the American gue uee’ss Rookie Roo o ki kiee of o the League’s Mos M ostt Valuable os Valu Va luu Yearr andd Most yer. Hee hholds olds ol ds tthe h Player. jor Leag gue rrecords ecoo ec Major League itss in a it for most hit hits son (26 62 inn 2200 00 00 season (262 2004) easo ea sonns in so andd most sseasons ow with at at least le a row as of 22010). 2000 hits (10 as own here e: Suzuki Suzuk Su Shown here: okes a single sing si nglle in a ng strokes 2010 game. 15

Science at Work in Baseball

Heavy Bats, Light Bats To hit a home run, the batter needs to give the ball a lot of momentum. For this to happen, the bat has to have a great deal of momentum. Since momentum depends on mass, it might seem useful to use a really heavy bat. But there may be a problem with using a very heavy bat. Momentum also depends on velocity. It’s hard to swing a heavy bat very fast. Because of the second law of motion, a batter needs to use more force to accelerate a heavy bat. It’s much easier to swing a light bat fast. But here, too, there’s a problem. If the bat is too light, it won’t have enough mass to produce as much momentum as the batter may want. (Remember: momentum depends on both velocity and mass.) So what weight of bat is best? The answer partly depends on the batter. Batters who are strong and quick are able to swing a heavy bat fast. Home run king Babe Ruth used a bat weighing about 50 ounces (1,400 grams). Ruth ended his career in 1935. Since his time, coaches and players

Fast, Fast, Fast Giving the bat a lot of momentum is not the only reason a batter has to be able to swing the bat at a fast speed. The batter has a fraction of a second to react once the pitcher throws the ball. In order to hit a fair ball, the batter has to begin the swing at the right instant. If it is a few thousandths of a second too early or

16

too late, the ball will be hit foul or maybe even missed completely. Great batters can do all this—see the ball, react, and, if the pitch is good, swing—almost automatically. They stay alert but don’t get too tense. They don’t hold the bat too tightly. Tense, tight muscles act more slowly than relaxed ones.

16

Hit the Ball!

have found that a lighter bat gives the best results for most batters. Today’s Major League hitters tend to use a bat of about 30 ounces (850 grams).

Hitting for Power or Bat Control A power hitter trying to slug a home run needs to transfer a lot of momentum to the ball. The batter has to swing the bat with a lot of force. But this makes it harder to control the bat, meaning the batter is more likely to miss the ball. That’s why some home run hitters also strike out a lot. A star like Ichiro Suzuki prefers to focus on good bat control. He doesn’t swing quite as hard. As a result, he doesn’t hit a lot of homers. But he hits for a very high average. In some situations, a batter may want to just tap the ball in order to lay down a bunt. When good bat control is more important than giving the ball a lot of momentum, a light bat is better than a heavy one. It has less inertia. A light bat gives a hitter better bat control. This can be helpful when the hitter is trying to bunt.

17

CHAPTER

THREE

Choosing Pitches

Mariano Rivera is famous for getting batters out in the ninth inning with his cut fastball. 18

Choosing Pitches

M

ost pro pitchers can throw more than one type of pitch. When protecting a lead with two outs in the bottom of the ninth, they usually want to finish the game as quickly as possible. Pitchers in this situation want to avoid giving up a walk, so they try especially hard to keep their pitches in the strike zone. They tend to throw the pitch they can best control. For many pitchers, this is a fastball. But it also makes sense to keep the batter guessing about how fast, and where over the plate, the next pitch will be. A batter who guesses wrong about a pitch is more likely to swing and miss. Or the batter may hit the ball foul or hit a ball that can easily be caught for an out. For this reason, pitchers like to throw a variety of pitches to a batter. Even in the bottom of the ninth, a pitcher whose best pitch is a blazing fastball might try to trick the batter with a slower pitch, or changeup. Or the pitcher might throw a breaking ball. This kind of pitch curves, or breaks away, from the path that is followed by a fastball or by a normal changeup.

No Straight Lines Actually, even the swiftest fastball never travels in a perfectly straight line. Various forces affect the ball as it moves toward the batter. Obviously a strong wind can give a ball a big push. But even when there is no wind, even when the air is totally still, gravity keeps drawing every pitch downward. So every fastball follows a somewhat curved path. To allow for this, pitchers aim their pitches a bit above the spot in the strike zone where they want the ball to go. 19

Science at Work in Baseball

Spin, Spin, Spin Another force that affects every pitch is air resistance. It gradually reduces the ball’s speed as the ball moves toward the batter. But that isn’t all the air does. If the ball spins as it flies through the air, interesting things can happen to the path of the ball. When a ball spins, it turns around an imaginary line—called the axis—that runs through its center. Pitchers give the ball a particular spin by gripping and releasing it in a certain way. The spin can interact with the air to change the ball’s path. Say, for instance, a pitcher throws a fastball by holding the ball near the ends of the fingers and letting the ball roll off the fingers. This gives the ball backspin. In this type of spin, the back of the ball (the surface farthest from home plate) keeps rolling down and toward the front. Backspin results in an upward force on the ball as it speeds toward the batter. To the batter, a fastball with backspin may look like it rises up. Players often talk about a pitcher’s “rising fastball.” The fastball doesn’t actually rise. The pull of gravity is too strong for that. But the batter thinks the ball rises because the backspin makes it drop less than expected.

Breaking Balls Spin can make a ball curve, or break, in a sideways direction. Here are some common types of breaking balls: curveball: When thrown by a right-handed pitcher, the pitch curves downward and to the left. A left-hander’s curveball curves down and to the right. screwball: A curveball that breaks in the opposite direction. A right-hander’s screwball curves to the right. A left-hander’s screwball curves to the left. 20

Choosing Pitches

How the Pitcher Grips the Ball Fastball

1

Curveball

2

1

Screwball

1

2 Slider

2

1

2

How a pitcher grips and releases the ball can give it different kinds of spin and make it curve in different ways.

sinker: A type of fastball that drops more than the average fastball. slider: A pitch thrown faster than a curveball and with the wrist cocked at a right angle. It at first looks to the batter like a fastball, but then it suddenly breaks slightly. This pitch should be thrown only by adults, since the stress it puts on the shoulder, elbow, and wrist can damage a growing arm. This is also true of the cutter, or cut fastball, which is similar to the slider but faster. Spin produces its amazing results by affecting the air pressure around the ball. Air pressure is the force that the air applies to anything in it. At Earth’s surface the 21

Science at Work in Baseball

Knuckleball Magic The pitch known as the knuckleball may dance around in surprising ways. The movement is very unpredictable, making it hard for the batter to hit the ball. The ball is also hard for the catcher to catch. Not all knuckleball pitchers grip the ball with their knuckles.

No matter how the ball is gripped, the pitcher gives it little or no spin. This lets the raised stitches on the ball’s seams interfere with the flow of air around the ball. As a result, forces arise that nudge the ball here and there.

Knuckleball pitcher Tim Wakefield had won more than 190 Major League games by the end of the 2010 season.

air pressure is about 14.7 pounds per square inch (about 1 kilogram per square centimeter). People don’t notice this force because they are used to it, but it is there. When a spinning baseball flies through the air, the spin causes changes in the air pressure right next to the ball. These changes affect the ball’s path. The ball’s path tends to bend in the direction of the spin. Suppose a pitcher throws a fastball with a lot of backspin. As the ball spins, air next to the back of the ball gets pulled to below the ball. Air in front of the ball gets pulled to above the ball. The ball is not only spinning but is 22

Choosing Pitches

Magnus Force on a Spinning Ball

Magnus Force

Direction of Ball’s Spin

Velocity of Ball

Drag Axis

The Magnus force results from interaction between the ball’s spin and the air. This force pushes the ball in a direction that is at a right angle both to the ball’s velocity and to the axis of the spin.

rapidly moving forward. As a result, the air pressure under the ball tends to build up while the air pressure above the ball decreases. This produces a slight upward force, or lift. A pitched ball that is spinning from right to left or left to right (as seen by the pitcher) feels a force in a sideways direction. Suppose a ball is thrown so that it spins from left to right. As the ball heads toward home plate, the spin makes air pressure increase on its right side and decrease on the left. The ball curves to the left toward first base. This force that acts on a moving, spinning object is called the Magnus force. It is named after the German scientist (Heinrich Gustav Magnus) who described it. 23

CHAPTER

FOUR

In the Field

Outfielders often throw the ball with backspin and at an upward angle to help it travel farther. Shown here: Ryan Sweeney returns the ball to the infield after a hit. 24

In the Field

W

hen the batter hits a pitch and starts running the bases, the laws of physics stay in effect. The ball’s path depends on factors including its momentum, its spin, air resistance, and the force of gravity. Physics also governs how fielders play the ball and how base runners advance.

Fly Ball A fly ball obeys the branch of physics that deals with projectiles. A projectile is simply an object that is thrown or shot into the air. Cannonballs are projectiles. When a batter hits a ball into the air, the ball begins its flight at a certain velocity. This means that it is traveling at a certain speed in a certain upward direction. Physicists look at this velocity as a combination of two separate velocities. One is in a vertical direction—that is, straight up. The other is in a horizontal direction—parallel to the ground. The force of gravity always pulls downward. It affects only the vertical part of the ball’s velocity. Gravity’s pull makes the ball’s velocity upward gradually decrease. At some point the vertical velocity becomes equal to zero. This is when the ball is at the highest point. But gravity keeps pulling, and so the ball starts falling toward the ground. The acceleration from gravity now keeps trying to increase the downward velocity.

Air’s a Drag Gravity works only in one direction: down. But as long as the ball is moving, another major force also affects it. That force is air resistance, or drag. It acts no matter what direction the ball goes in. It works to lessen the ball’s vertical velocity, or its speed going up. It also gradually reduces the 25

Science at Work in Baseball

Speed Limit When two or more forces act on an object at the same time, they may work together or they may work against each other. It all depends on the directions the forces act in. If a baseball is hit or thrown straight into the wind, the force of the wind adds to the regular drag force from the air and makes the ball slow down more quickly. If the ball moves in the same direction as the wind, the wind reduces the drag, and the ball slows down less quickly. Here’s a different example: a baseball falling through the air. Let’s

say there is no wind, so we don’t have to worry about that. The force of gravity keeps pulling on the ball, causing it to go faster and faster toward the ground. As it goes faster, the drag force of the air gets bigger. Since the ball is moving downward, the drag works against gravity. When the ball reaches a certain speed, the drag becomes so great that gravity can’t make the ball fall any faster. This speed is called the ball’s terminal speed, or terminal velocity. For a baseball, it is about 74 miles per hour (33 meters per second).

ball’s horizontal velocity while the ball is in the air. As a result, the fly ball doesn’t go as high as it would if there were no air. It also doesn’t travel as far before it hits the ground as it would if there were no air.

Playing the Angles Some experts say fly balls generally go farthest when they are hit at an angle of about 35 degrees. But that’s not the whole story. A ball flying off a bat may have a lot of spin. Hitting the ball below the ball’s center tends to create backspin. Hitting it above its center tends to produce topspin (the opposite of backspin). If the ball has backspin, it can receive considerable lift and may go much farther than would a ball with no spin. On the other hand, topspin can make the ball drop faster than it otherwise would. Angles and spin are also important for fielders’ throws. Fielders may put backspin on their throws to make the ball 26

In the Field

Flight of a Fly Ball

250 feet 175 feet

With Air Drag

0 feet

325 feet

With No Air Drag

580 feet

Air drag resists a ball’s motion. If there were no air, a fly ball would go farther and higher.

go farther. How far a throw travels also depends on the angle at which the ball is thrown. If a throw is flat, gravity will quickly pull the ball down. For this reason, an outfielder throwing to the infield or a third baseman throwing across the infield to first will often arc the ball, throwing it at an upward angle rather than in a straight line.

More About Air How far a fly ball travels depends on its momentum, its spin, and the angle at which it left the bat. These are all features of the ball. Features of the air can also affect the ball’s flight. Wind is one of these features. Hitters need to know in what direction the wind is blowing during a game. Suppose, 27

Science at Work in Baseball

Stadium Quirks It’s easier to hit a home run in some stadiums simply because the outfield wall is closer to home plate. In Fenway Park, where the Boston Red Sox play, the left-field wall is only 310 feet (94.5 meters) from home plate down the left-field line. On the other hand, it takes a high

fly ball to clear this wall. At 37 feet (11.3 meters), the wall is unusually tall. It has been nicknamed the Green Monster. Balls that fail to clear the top sometimes bounce off the wall in odd ways.

A fly ball must be hit very high in the air to make it over the Green Monster at Fenway Park.

for example, the wind is blowing toward home plate in right field but is blowing out of the stadium in left. A batter trying to hit a home run should try to hit the ball to left. The air’s density—how thick or thin it is—also affects how far a ball may travel. Air is made of particles of gases, such as oxygen. When air gets denser, the particles come closer together. This increases the air’s drag on a baseball. Cold air is denser than warm air. For this reason, the ball flies farther when the temperature is high. It carries better in hot weather than in cold, and better during the day than at night. Dry air is denser than moist air, so the ball goes farther when the weather is humid. Air at low altitudes is denser than air at high ones. As a result, balls tend to carry farther at Denver’s Coors Field than at Baltimore’s Oriole 28

In the Field

Juan Pierre uses a head-first slide to steal second base.

Park at Camden Yards. Denver is about one mile (1.6 kilometers) above sea level. Oriole Park is near sea level.

Friction for Speed Surfaces produce friction. This is a force that resists the motion of an object across the surface. Friction comes in handy for base stealers. Runners trying to steal want to get to the base as fast as possible. They ordinarily can’t run full steam to the base, however. If they did that, they very likely would not be able to stop until after they crossed the base. Then they might be tagged out. Instead, runners often slide into the base. By sliding, they make use of the force of friction to stop quickly.

Rounding the Bases Base runners trying to advance two or more bases follow a rounded path. It would be shorter to run straight up to a base, turn sharply toward the next base, and then run straight to that one. But they don’t do that because it would require them to spend a lot of effort to overcome their inertia. Because of the first law of motion, a runner would have to

exert force to make each stop, each sharp turn, and each new start. Doing this would waste time. By going in a rounded path, runners can keep going at a good pace and do not lose time fighting their own inertia at each base. They can get from, say, first to third or from second to home faster even though they’re running a slightly longer distance. 29

Science at Work in Baseball

GLOSSARY

acceleration: A change in velocity. As a measurement, it is the rate at which velocity changes. axis: In a spinning ball, the imaginary line running through the ball’s center around which the ball turns. backspin: A type of spin in which the back of a ball rolls down and toward the front. It is the opposite of topspin. conservation: In physics, the idea that something cannot be destroyed. For example, energy is always conserved, but it may change from one form to another. density: How close together the particles are that make up a gas. Air with particles that are close together is denser than air where there is more space between the particles. drag: Air resistance; a force that slows an object moving through the air. energy: In physics, the ability to do work. force: Anything that causes a change in the velocity of an object, such as a push or a pull. friction: A force resisting the movement of an object across a surface. gravity: A force that pulls objects toward the center of Earth. inertia: The tendency of an object to resist being accelerated. A force has to be applied in order to put into motion an object that is at rest or to change the velocity of an object that is moving. kinetic energy: The energy of a moving object. Magnus force: A force that acts on a moving object that is rapidly spinning. It pushes the object sideways relative to the axis of the spin. mass: The amount of matter in an object. momentum: A measure of an object’s motion. It equals the object’s mass multiplied by its velocity. physics: The branch of science dealing with matter and energy. Scientists who work in physics are called physicists. They study such things as moving objects. projectile: An object that has been put into motion in the air by some force. resistance: Opposition to the movement of an object. topspin: A type of spin in which the front of a ball rolls down and toward the back. It is the opposite of backspin. 30

velocity: In physics, the speed and direction of a moving object. Some people use the word to mean simply “speed.”

FIND OUT MORE

Bottom of the Ninth

BOOKS Bonnet, Robert L., and Dan Keen. Home Run! Science Projects with Baseball and Softball. Berkeley Heights, NJ: Enslow, 2009. Bow, James. Baseball Science. New York: Crabtree, 2009. Gifford, Clive. Baseball. New York: Marshall Cavendish Benchmark, 2010. Mercer, Bobby. The Leaping, Sliding, Sprinting, Riding Science Book: 50 Super Sports Activities. New York: Lark Books, 2006. Teitelbaum, Michael. Baseball. Ann Arbor, MI: Cherry Lake, 2009. Thomas, Keltie. How Baseball Works. Toronto, Ontario: Maple Tree Press, 2008. Whiting, Jim. The Science of Hitting a Home Run. Mankato, MN: Capstone Press, 2010.

WEBSITES www.exploratorium.edu/baseball/ index.html The website of the Exploratorium, a science museum in San Francisco, California, highlights several aspects of the science of baseball and includes science experiments. http://entertainment.howstuffworks.com/ baseball.htm This website gives a good summary of the basics of baseball. http://mlb.mlb.com/index.jsp This is the official website of Major League Baseball. It is packed with data on teams, players, and games. It is also a great place to learn the official rules. www.projectview.org/MathandBaseball/ ScienceattheBallgame.htm The Schenectady, New York, school system sponsors this website, which gives information on the physics of pitching, batting, and baserunning.

31 31

Science at Work in Baseball

INDEX

Page numbers in bold type are for photos, charts, and illustrations. acceleration, 13–14, 16, 25 air pressure, 21–23, 23 air resistance (drag), 11, 20, 24, 25, 26, 27, 28 angles, 24, 26, 27 axis, 20, 23 backspin, 20, 22, 26 baseball field diagram, 9 base runners, 29 bats and bat control, 8, 12, 13, 16–17, 17 batters and batting, 5, 5, 7, 8, 12, 13, 15, 16, 17, 17 breaking balls, 19, 20–22, 21 Cabrera, Miguel, 5 changeup, 19 conservation of energy, 10 curveball, 20, 21 density (air), 28–29 drag. See air resistance (drag) energy, 7, 10 fastball, 6, 18, 19, 20, 21, 22 first law of motion, 8, 9–10, 29 fly balls, 25–27, 27, 28 force (physics), 10, 11, 13, 14, 23, 23, 25, 29 friction, 29 gravity, 11, 25, 27 helmets, 7 home runs, 5, 12, 16, 17 horizontal velocity, 25–26 inertia, 14, 29 kinetic energy, 7

knuckleball, 22, 22 laws of motion, 8–11, 13, 14, 29 Lincecum, Tim, 4 Magnus force, 23, 23 mass, 14, 15, 16 momentum, 14, 15, 16, 27 Newton, Isaac, 8 ninth inning, 5, 13, 18, 19 physics, 8, 25 Pierre, Juan, 29 pitchers and pitching, 4, 5, 7, 11, 18, 19–23, 21, 22, 23 projectiles, 25 radar gun, 6, 6 Rivera, Mariano, 18 Ruth, Babe, 12, 16 screwball, 20, 21 second law of motion, 13, 14 sinker, 21, 21 slider, 21, 21 sliding, 29, 29 speed of ball, 6, 6, 11, 19, 20, 26 spins and spinning, 20–23, 21, 23, 26 stadiums, 28, 28, 29 strike zone, 5, 5–6, 19 Suzuki, Ichiro, 15, 15, 17 Sweeney, Ryan, 24 topspin, 26 velocity, 8, 10, 13, 16, 23, 25–26 vertical velocity, 25 Wakefield, Tim, 22 wind, 19, 26, 27–28

About the Author Richard Hantula has written, edited, and translated books and articles on science and technology for more than three decades. He was the senior U.S. editor for the Macmillan Encyclopedia of Science. 32