How Does a Baseball Bat Work Alan M' Nathan, UIUC anathanuiuc'edu www'npl'uiuc'eduanathanpob

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How Does a Baseball Bat Work?Alan M. Nathan,
UIUCa-nathan_at_uiuc.eduwww.npl.uiuc.edu/a-nathan/
pob

• My day job
• experimental nuclear/particle physics
• high-speed collisions between subatomic particles
• Nights and weekends...
• physics of baseball
• high-speed collision between baseball and bat

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Hitting the Baseball
...the most difficult thing in sports --Ted
Williams
BA .344 SA .634 OBP .483 HR 521
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Heres Why..

• 90 mph fastball takes about 0.40 sec to reach
  batter
• 0.20 sec needed to observe, process, decide
• 0.15 sec needed for swing
• half of break occurs in last 0.10 sec
• if batter mis-estimates speed by ?1.5 mph (0.007
  sec)
• swing will be early/late by 1
• elevation of ball misjudged by ?1
• backspin/topspin makes ball fall less/more
• Warren Spahn (greatest lefthander?) said
• Hitting is timing. Pitching is upsetting
  timing.
• 30 success rate gets you in Hall of Fame!

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The Ball-Bat Collision

• forces large (gt8000 lbs!)
• time is short (lt1/1000 sec!)
• ball compresses, stops, expands
• bat compresses ball.ball bends bat
• bat is very flexible!
• hands dont matter!
• GOAL maximize hit ball speed
• 1 mph ? 4-5 ft

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What Does Hit Ball Speed Depend On?

• Pitched ball speed and swing speed of bat
• bat matters much more
• Weight of bat
• also the weight distribution
• Bounciness of ball
• is it juiced?
• Impact location along bat
• sweet spot

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Wood versus Aluminum

• Thin shell .
• fatter barrel, thinner handle
• trampoline effect
• golf drivers
• tennis rackets
• corked bats?
• ping vs. crack
• lighter
• CG closer to handseasier to swing
• Regulation of bat performance

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Summary

• Lots of physics in baseball-bat collision
• Knowledge of physics helps understanding of game
• And its fun too.