Introduction When Ash Meets Cowhide The Aerodynamics of Baseball The Art of Pitching Summary - PowerPoint PPT Presentation

Slide1 l.jpg
Download
1 / 37

  • 316 Views
  • Updated On :
  • Presentation posted in: Sports / Games

Baseball 101: A Primer on the Physics of Baseball Alan M. Nathan Saturday Physics Honors Lecture October 21, 2000. Introduction When Ash Meets Cowhide The Aerodynamics of Baseball The Art of Pitching Summary. REFERENCES.

Related searches for Introduction When Ash Meets Cowhide The Aerodynamics of Baseball The Art of Pitching Summary

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

Download Presentation

Introduction When Ash Meets Cowhide The Aerodynamics of Baseball The Art of Pitching Summary

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Slide1 l.jpg

Baseball 101: A Primer on the Physics of BaseballAlan M. NathanSaturday Physics Honors LectureOctober 21, 2000

  • Introduction

  • When Ash Meets Cowhide

  • The Aerodynamics of Baseball

  • The Art of Pitching

  • Summary


References l.jpg

REFERENCES

  • The Physics of Baseball, Robert K. Adair (Harper Collins, New York, 1990), ISBN 0-06-096461-8

  • The Sporting Life, Davis and Stephens (Henry Holt and Company, New York, 1997), ISBN 0-8050-4540-6

  • http://www.exploratorium.edu/sports

  • ME!

    • a-nathan@uiuc.edu

    • http://www.npl.uiuc.edu/~a-nathan/pob


Slide3 l.jpg

1927 Yankees:

Greatest baseball team

ever assembled

1927

Solvay Conference:

Greatest physicsteam

ever assembled

Baseball and Physics: Murderers Rows of 1927


Hitting the baseball l.jpg

#521, September 28, 1960

Hitting the Baseball

“...the most difficult thing to do in sports”

--Ted Williams,

Professor of Hitting

BA: .344

SA: .634

OBP: .483

HR: 521

all time leader


Slide5 l.jpg

Here’s Why…..

(Courtesy of Robert K. Adair)


Trivia timeout l.jpg

correct

Trivia Timeout

  • Rogers Hornsby is one of only two players to have won the Triple Crown twice. Who is the other player?

    A) Hank Aaron

    B) Mickey Mantle

    C) Carl Yastrzemski

    D) Ted Williams


Slide7 l.jpg

When Ash Meets Cowhide

  • A violent collision!

    • forces large (>8000 lbs!)

    • time is short (<1/1000 sec!)

    • ball compresses, stops, expands

    • kinetic energy  potential energy

    • lots of energy dissipated (friction)

  • hands don’t matter!

  • GOAL: maximize ball exit speed vf

    vf 105 mph  x  400 ft x/vf = 4-5 ft/mph

What aspects of collision lead to large vf?


Speed of hit ball what does it depend on l.jpg

Speed of Hit Ball:What does it depend on?

  • The basic stuff (“kinematics”)

    • speed of pitched ball

    • speed of bat

    • weight and weight distribution of bat

  • The really interesting stuff (“dynamics”)

    • “bounciness” of ball

    • vibrations of bat


What determines batted ball speed l.jpg

collision efficiency

(property of ball/bat)

vf =  vball + (1+) vbat

What Determines Batted Ball Speed?

  • How does batted ball speed depend on ...

    • pitched ball speed?

    • bat speed?

For typical collision on fat part of bat,

=0.2 1+ = 1.2

Conclusion:

Bat Speed Matters Much More!

Question: What properties of ball/bat determine ?


What determines batted ball speed10 l.jpg

.

CM

.

recoil

What Determines Batted Ball Speed?

  • Mass of bat


What determines batted ball speed11 l.jpg

.

.

CM

rotation

recoil

What Determines Batted Ball Speed?

  • Mass of bat

Mass distribution of bat


Slide12 l.jpg

(½ mv2)

What is the Ideal Bat Weight?

Conclusion: More data needed to determine optimum bat weight.


Slide13 l.jpg

Trivia Timeout

  • Who is this guy and what was his number?

Eddie Gaedel…1/8


The c oefficient o f r estitution energy dissipation in ball l.jpg

This is COR2

The Coefficient of Restitution:Energy Dissipation in Ball

  • COR measures “bounciness” of ball

  • Final speed/Initial speed

  • For baseball, COR 0.5

    • hf/hi = 3/4

    • 3/4 energy lost!

  • Is the ball “juiced”?


Slide15 l.jpg

COR and the “Juiced Ball” Issue

MLB:COR=0.546  0.032

@ 58 mph on massive rigid surface


Effect of bat on cor trampoline effect l.jpg

tennis ball/racket

Effect of Bat on COR:“Trampoline” Effect

  • Energy shared between ball and bat

  • Wood Bat: nearly incompressible

    • ~ 2% of energy stored in bat

    • Efficiently restored to ball

      • BPF~ 1

  • Aluminum Bat

    • ~ 10-20% energy stored in bat

    • Efficiently restored to ball

    • Result: “trampoline effect”

      • BPF ~ 1.1-1.2

      • Ball fliesoff the bat!

Bat Performance Factor:

COReffective/COR

new NCAA rules:<.228


Slide17 l.jpg

correct

Trivia Timeout

  • Who is this guy?

    A) Joe Torre

    B) Don Zimmer

    C) Lou Skizas

    D) Roger Maris


Effect of bat on cor bat vibrations l.jpg

Effect of Bat on COR: Bat Vibrations

  • Collision excites bending vibrations in bat

    • Ouch!! Thud!!

    • Sometimes broken bat

    • Energy lost  lower COR


Slide19 l.jpg

f1 = 177 Hz

1st mode

nodes

2nd mode

f2 = 583 Hz

0-20 ms

Shape of vibration

Time profile of vibration

Vibrational Modes of Bat

Louisville Slugger R161 (33”, 31 oz)

This can be measured!


Putting it all together l.jpg

nodes

Center of mass

Putting it all together….


Possible physics sweet spots l.jpg

Possible “Physics Sweet Spots”

  • Center of Percussion (~6”)

  • Node of lowest vibration (~6”)

  • Maximum hit ball speed (~5”)

  • Minimum total vibrations (~5”)

Question: Where is “batters sweet spot”?


Advantages of aluminum l.jpg

Advantages of Aluminum

  • Length and weight “decoupled”

    • Can adjust shell thickness

    • Fatter barrel, thinner handle

    • Lighter

      • Higher bat speed

    • More of weight closer to hands

      • Easier to swing

      • Less rotational recoil

      • More forgiving on inside pitches

  • More compressible => “springier”

    • Trampoline effect, higher COR

  • Stiffer for bending

    • Less energy lost due to vibrations


Slide23 l.jpg

correct

Trivia Timeout

  • Who is the only player to steal five bases in one game?

    A) Ricky Henderson

    B) Lou Brock

    C) Tony Gwynn

    D) Ty Cobb


Aerodynamics of a baseball l.jpg

Aerodynamics of a Baseball

Forces on Moving Baseball

  • No Spin

    • Boundary layer separation

    • DRAG!

    • Grows with v2

  • With Spin

    • Ball deflects wake

    • action/reaction  Magnus force

      • Force grows with rpm

      • Force in direction front of ball is turning


The flight of the ball real baseball vs physics 101 baseball l.jpg

The Flight of the BallReal Baseball vs. Physics 101 Baseball

  • Role of Drag

  • Role of Spin

  • Atmospheric conditions

    • Temperature

    • Humidity

    • Altitude

    • Air pressure

    • Wind


The role of friction l.jpg

The Role of Friction

  • Friction induces spin for oblique collisions

  • Spin => Magnus force

  • Results

    • Balls hit to left/right break toward foul line

    • Backspin keeps fly ball in air longer

    • Topspin gives tricky bounces in infield

    • Pop fouls behind the plate curve back toward field


The home run swing l.jpg

The Home Run Swing

  • Ball arrives on 100 downward trajectory

  • Big Mac swings up at 250

  • Ball takes off at 350

    • The optimum home run angle!


The art of pitching l.jpg

“Hitting is timing. Pitching is upsetting timing”

---Warren Spahn

vary speeds

manipulate air flow

orient stitches

Don Larsen, 1956 World Series

Last pitch of perfect game

The Art of Pitching


Trivia timeout29 l.jpg

Who is standing behind Don Larsen?

A) Bobby Richardson

B) Tony Kubek

C) Billy Martin

D) Yogi Berra

Don Larsen, 1956 World Series

Last pitch of perfect game

correct

Trivia Timeout


Slide30 l.jpg

7

6

Vertical Position of Ball (feet)

5

90 mph Fastball

4

3

0

10

20

30

40

50

60

Distance from Pitcher (feet)

1.2

1

75 mph Curveball

0.8

Horizontal Deflection of Ball (feet)

0.6

0.4

0.2

0

0

10

20

30

40

50

60

Distance from Pitcher (feet)

How Much Does the Ball Break?

  • Depends on…

    • Magnitude and direction of force

    • Time over which force acts

  • Calibration

    • 90 mph fastball drops 3.5’ due to gravity alone

    • Ball reaches home plate in ~0.45 seconds

  • Half of deflection occurs in last 15’

  • Drag reduces fastball by about 8 mph

  • Examples:

    • Hop of 90 mph fastball: ~4”

    • Break of 70 mph curveball ~16”

      • slower

      • force larger


Example 1 fastball l.jpg

Example 1: Fastball

85-95 mph

1600 rpm (back)

12 revolutions

0.46 sec

M/W~0.1


Example 2 split finger fastball l.jpg

Example 2: Split-Finger Fastball

85-90 mph

1300 rpm (top)

12 revolutions

0.46 sec

M/W~0.1


Example 3 curveball l.jpg

Example 3: Curveball

70-80 mph

1900 rpm

(top and side)

17 revolutions

0.55 sec

M/W~0.25


Example 4 slider l.jpg

Example 4: Slider

75-85 mph

1700 rpm (side)

14 revolutions

0.51 sec

M/W~0.15


Effect of the stitches l.jpg

Effect of the Stitches

  • Obstructions cause turbulance

  • Turbulance reduces drag

    • Dimples on golf ball

    • Stitches on baseball

  • Asymmetric obstructions

    • Knuckleball

    • Two-seam vs. four-seam delivery

    • Scuffball and “juiced” ball


Slide36 l.jpg

Trivia Timeout

Who said...

  • "Baseball is 90% mental. The other half is physical."

  • "You can observe a lot by watching."

  • "If the people don’t want to come out to the park, nobody’s going to stop them."

  • "No one ever goes to that restaurant any more. It’s too crowded."


Summary l.jpg

Summary

  • Much of baseball can be understood with

    basic principles of physics

    • Conservation of momentum, angular momentum, energy

    • Dynamics of collisions

    • Trajectories under influence of forces

      • gravity, drag, Magnus,….

  • There is probably much more that we don’t understand

  • Don’t let either of these interfere with your

    enjoyment of the game!


  • Login