The Flight of a Baseball

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The Flight of a Baseball
Alan M. Nathan, University of Illinois a-nathan_at_il
linois.edu http//go.illinois.edu/physicsofbasebal
l

• Introduction
• PITCHf/x and HITf/x
• Using baseball to learn about physics
• Using physics to learn about baseball
• -how pitchers do what they do
• -how batters do what they do

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Forces on a Spinning Baseball in Flight

• Drag slows ball down
• Magnus mg deflects ball from straight line

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Real vs. Physics 101 Trajectory Effect of
Drag and Magnus
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PITCHf/x and HITf/x

• Two video cameras _at_60 fps
• high home and high first
• tracks every pitch in every MLB ballpark
• all data publicly available on web!
• tracks initial trajectory of batted ball
• Used for analysis, TV broadcasts, MLB Gameday,
  etc.

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So what good is a physicist in all this?

• Minimal parametrization of the trajectory
• Constant acceleration works very well for pitched
  ball
• Batted balls ???
• Determining Magnus acceleration
• spin movement important for studying pitching
• Dealing with noisy data, miscalibrations, etc.
• Keeping everyone honest
• Measurements have uncertainties!

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Baseball AnalysisUsing PITCHf/x to discover
how pitchers do what they do
Hitting is timing. Pitching is upsetting
timing.
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Ex 1 Mariano Rivera Why is he so good??
Three Reasons Location, Location, Location
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Ex 2 Late Break Truth or MythMariano
Riveras Cut Fastball
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Ex 2a What makes an effective slider
Josh Kalk, THT, 5/22/08
This slider is very effective since it looks like
a fastball for over half the trajectory, then
seems to drop at the last minute (late break).
side view
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Ex 3 A Pitchers Repertoire LHP Jon Lester,
August 2007
Catchers View
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Ex 4 Jon Lester vs. Brandon Webb
15 inches
Brandon Webb is a sinkerball pitcher Almost no
rise on his fastball
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Ex 5 The Knuckleball
Tim Wakefield is a knuckleball pitcher Chaotic
Movement
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Studies of Batted Balls

• HITf/x ? v0,?,?
• Hittracker (Greg Rybarczyk)
• Landing point
• Flight time
• Together these constrain the full trajectory

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Hitting a Long Fly Ball
R vs. v0
R vs. ?0
USEFUL BENCHMARK 400 ft _at_ 103 mph 5 ft per mph
peaks _at_ 25o-35o
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What Constitutes a Well-Hit Ball?
w/o home runs
home runs
V0gt90
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Putting Spin on Batted Balls

• undercutting/overcutting ? backspin/topspin
• upward/downward Magnus force
• In front or behind ? sidespin
• sideways Magnus force

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Some Familiar Effects Due to Spin

• Balls hit to left/right break toward foul line

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Extract sidespin vs. ? from trajectory
CF
RF
LF
RF
LF
RF
LHH
RHH
?

• Balls break toward foul pole
• Break increases with angle
• Ball hit to CF slices
• LHH/RHH asymmetry
• Tilt in bat

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Some Familiar Effects Due to Spin

• Balls hit to left/right break toward foul line
• Topspin makes line drives nose-dive
• Backspin keeps fly ball in air longer
• Tricky popups to infield

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Paradoxical Popups
Watch for fielders confusion and for bounce of
ball
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HITf/xhittracker Analysis The carry of a
fly ball

• Motivation does the ball carry especially well
  in the new Yankee Stadium?
• carry (actual distance)/(vacuum distance)
• for same initial conditions

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HITf/x hittracker Analysis4354 HR from 2009
Denver
Cleveland
Yankee Stadium
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Summary

• We are on the verge of major breakthrough on
  our ability to track baseballs and determine the
  aerodynamic effects
• The new tools I have discussed are already
  revolutionizing baseball analysis
• And the tools are getting better.
• So, fun times ahead for me

shown here doing experimental baseball physics