Out of the Park: The Physics of Baseball | KQED QUEST


[MUSIC PLAYING] Still looking for his
first collegian home run. 1-0 pitch– line drive
down the left-field line. Baseball, America’s
favorite pastime. Most people think they
know the basic rules of the game– the pitcher
throws, the batter hits, three strikes and you’re out. But underneath it all, the rules
that truly govern this game are the laws of physics. When you go to a
ballgame, you’re seeing all the interplay
of force and velocity and projectile motion. It’s a beautiful thing
to see and watch. Paul Robinson is
a physics teacher at San Mateo High School
and a rabid baseball fan. He uses the sport to
teach his students about how the universe works. Physics is a beautiful way to
see the world that we live in. Being a student of
physics just makes the game that much more
interesting and fascinating. A 95-mile an hour fastball
will reach home plate in four tenths of a second. If you’re a student
of physics, it’s likely you’re familiar with
this place– UC Berkeley. Home to eight Nobel Prize
winners, the physics department at Cal is second to none. But if it’s the physics
of baseball you’re after, the best place for
your field work is on the other side of campus. We brought in a
couple of ringers to show us what’s going on. Hi, I’m Linda Shore. And I’m David Barker. I’m a physicist, and we both
work at the Exploratorium in San Francisco. And we’re here at
Cal Berkeley campus, Evans Diamond, home of the
Cal Bears baseball team. And Linda, I bet you did
not know that there’s a physics laboratory out there. Well, I wouldn’t have
immediately thought about that. But I do know there’s a lot
of physics going on out there. I think what I
want to do, though, is learn how to throw
a baseball properly. So I think I’m going to spend
some time with the Cal pitching coach here and see
what he can teach me. And my swing has been
like a rusty gate lately. My power numbers are down. So I think I’m going to go
talk to the batting coach and see what I can learn. OK, well good luck to you. All right. Good luck to you, too. [MUSIC PLAYING] Instead of a
pushing motion where I’m leading with my
elbow, I’m trying to get here, get on
top of the baseball. What I mean by that is– Dan Hubbs is the pitching
coach for the Cal Bears. It’s his job to teach his
players how to get the most out of their pitching motion. With my fingers and kind of
let my lower half do the work and let my arm just kind
of go for a ride and make the ball spin. You know, as a physicist,
when I think about that, I’m now realizing that
what it really is about is momentum, that I
have these big body parts at the bottom of my
body– my legs and my hips. Right. And if I can turn those first
and get those in motion first, then I can have that momentum go
up my body to the smaller body parts that have less mass. I get more speed. Up the arm– less
mass, more speed. Fingers, hardly any
mass, a lot of speed. So it sounds like
it’s a whip motion. Right. That’s exactly right. It’s a lot like a whip. So I’m sort of going like that. That’d be right. We want to use our legs. We want to use our abs. We want to use our core
to throw the baseball. And then the phrase
we like to use is let your arm just
kind of go for the ride. But sending your
arm on that ride is a surprisingly complex task. if you really want
to see what works, watch someone who can
throw some real heat. Using a 3D, high-speed,
infrared, eight-camera motion analysis system, we can
see just how intricate the throwing motion is. The players wear reflective
markers, which the computer can pick up, calculating exact
body angles, joint velocities, and timing. It can also analyze the physical
kinetics or joint forces and torques placed on the body. For big leaguers like San
Francisco Giants ace Barry Zito, seeing this
can help them make subtle changes in biomechanics
to enhance performance and reduce injuries. Baseball pitchers are a
great experimental physicist because they’re constantly
trying this, trying that to see what works. Swing and a miss
by [? Garfin. ?] So just like that– Newton’s second law
of motion tells us that the acceleration
of an object is dependent upon
two things– its mass and how much net
force is acting on it. Translated, the harder you
throw, the faster it goes. But pitching takes more
than throwing hard. There are also external
forces in play. Each pitch is fighting
gravity and friction. When a pitcher
throws a ball, it has to push the air out of the way. And when it leaves
the pitcher’s hand, it’s going as fast
as it’s going to go. From that point on,
friction slows it down. As a ball moves
through the air, it’s very similar to a swimmer
swimming in water. The swimmer has to push
the water out of the way. The water pushes
back on the swimmer. While external forces may cut
down on momentum and velocity, a good pitcher will be able
to use this to his advantage. Friction and gravity can make
the ball do nasty things. Strike three called. A curveball will spin
up to 30 times a second and break as much as 17 inches. Why does a curveball curve? For many, many years,
it was actually thought to be an
optical illusion. But it really does curve. How much depends on how
fast you spin the ball. When a ball spins, it generates
greater pressure on one side as it moves through the
air than on the other side. And this difference in
pressure is a form of lift. It’s called the Magnus effect. So how do you get
a ball to curve? Well, we use finger
pressure on the baseball. So let’s say we have
the baseball here. What we try and do is we
may try finger pressure with our middle finger here
and let the ball– generally, the ball will break away
from you finger pressure. Now, what does the pressure do? It actually makes the
ball spin, doesn’t it? It makes the ball spin
a little differently. OK. So if it’s spinning like
this, this turbulent air that surrounds the ball gets
pushed in this direction. And so like a jet,
the ball is then forced to move in
this direction. So then you’ll get a
breaking ball like this. So really, I guess
all a batter has to do, if they can manage
it, is try to figure out what direction the
front of the ball is spinning because that’s the
direction that the ball’s going to curve. Bases loaded, two outs. Baseball is a game
of small differences. And it’s all about timing. And so the pitcher’s
doing everything he can to throw off the
timing of that batter. A splitter looks like a
fastball until velocity is lost and the bottom drops out. Time to step up to the plate. Newton’s third law of motion
states for every action, there is an equal and
opposite reaction. Welcome to the world of hitting. [MUSIC PLAYING] Once the ball leaves
the pitcher’s hand, the batter has less
than a half a second before it crosses the plate. This is going to be a base hit. This will at least
tie the game– You’ve got to decide
swing, dont’ swing. What kind of ball? Curveball, fastball, slider? You’ve got to make all those
decisions in 0.2 seconds. It’s almost a reaction
instead of a thought process. Some say it’s the hardest
thing to do in sports. Round bat hitting a round
ball– that’s not easy. Coach Jon Zuber, a
former major leaguer and a member of the
Cal hall of fame is an expert on teaching
the art of hitting. Then we let the body follow. And that’s when we get our
momentum out towards the– So you’re almost moving
your hips and your hands at the same time. Should you have a heavy
bat and a big long swing– like a big home run cut,
swinging from your heels? Or is it better to have a
short, compact stroke that relies upon bat speed
more than anything else? Do you have a theory on that? Well, I think bat speed
is the key to power. I need my hands to get from
there to there short and quick, as fast as possible. Exactly. So I need this weight
and that muscle and torque and force–
whatever you want to call it– to bang into that. And now I have a whole lot
of stuff hitting the ball at the same time, which
is going to propel it out towards the field. In the olden days,
bats were heavier. They were bigger, longer. Nowadays, they’re
shorter and lighter. And the reason for that
is so that the batter can get the bat going
as fast as possible. In terms of physics, it’s
actually a trade-off. The heavier the bat,
the faster the ball is going to come off the bat. That’s one thing. But the other thing is,
the heavier the bat, the harder it is to
get it to go fast. Hernandez hits a high
drive to left field. And you can forget
about that one. The collision of a ball on the
bat lasts only about 1/1,000 of a second. In an instant, the
batter can exert up to 8,000 pounds of
force on the baseball. What determines the
force that a bat hits the ball are two
things, primarily– how fast the ball was
pitched and how fast the batter swings the bat. But when those two
collide, it causes the ball to squish up to almost,
not quite half of its size. And it compresses like a spring. And then in a
thousandth of a second, it springs off the
bat, leaving faster than it came in, maybe 110 or
as much as 120 miles an hour. So is there like a
particular place on the bat that’s the best to
try to hit the ball? Yeah, you want to try to hit on
what they call the sweet spot. And the sweet spot is– on
metal bats or on aluminum bats, it’s a little bit bigger
than it is on the wood bat. But on a wood bat, it’s
generally right in this area, right in here. When you ring a
bell, it vibrates– or you hit a gong or
something like that. You can see it vibrating. When a ball hits a bat, the
bat actually vibrates, too. But there’s a point on the
bat where it doesn’t vibrate. It’s a so-called node. The sweet spot relates
to the nodes on the bat. A node is the point
along a standing wave where the wave has
minimal amplitude. When a ball hits a bat, it
causes waves of vibration. So if a hitter gets the
sweet spot onto the ball, there’s less
vibration, and the bat imparts all that kinetic
energy into the hit. If you hit the ball right on the
sweet spot, right about here, then all of the
angular momentum, all the swing of the bat
is going into the ball. The bat’s not rattling
around like this. So that’s also like when
you hit one really good on the sweet spot. It just– it’s got
that nice sound. It’s sort of like a very
quiet cracking sound. You need to know
where the nodes are. Baseball resonates through
multiple aspects of science. There’s classical mechanics,
fluid dynamics, biology, and don’t forget chaos theory. So maybe next time you’re
at a baseball game, don’t just pay
attention to the game. Look around and try to
find some of the science and mathematics, the
physics, the physiology, the biomechanics because there’s
really a lot of good science and math going on here. And as the great baseball
philosopher Yogi Berra once said, you can observe
a lot just by watching.

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