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1. Can a curveball be hit farther than a fastball? Some Aerodynamics

F L (Magnus). . Drag: F d = ½ C D Av 2. “Lift”: F L = C M ARv. F d. mg. 1. Can a curveball be hit farther than a fastball? Some Aerodynamics. (in direction leading edge is turning). C D , C M ~ 0.2-0.5. Motion Capture System. Two-wheel pitching machine.

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1. Can a curveball be hit farther than a fastball? Some Aerodynamics

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  1. FL(Magnus)  Drag: Fd = ½ CDAv2 “Lift”: FL= CMARv Fd mg 1. Can a curveball be hit farther than a fastball?Some Aerodynamics (in direction leading edge is turning) CD, CM ~ 0.2-0.5 NSBP Meeting, February 18, 2005

  2. Motion Capture System Two-wheel pitching machine Baseball with reflecting dot Measurements of Lift and DragJoe Hopkins, Lance Chong, Hank Kaczmarski, AMN NSBP Meeting, February 18, 2005

  3. y z Experiment: MoCap Data y = ½ ayt2 topspinay>g NSBP Meeting, February 18, 2005

  4. 77’ Effect of Spin on Baseball Trajectory • Lift … • scales approx. linearly with  • has major effect on trajectory NSBP Meeting, February 18, 2005

  5. Oblique Collisions:Putting Spin on the Ball Sliding friction … • reduces transverse velocity • increases  • sliding-to-rolling transition Results • Balls hit to left/right break toward foul line • Topspin gives tricky bounces in infield • Pop fouls behind the plate curve back toward field • Backspin keeps fly ball in air longer f NSBP Meeting, February 18, 2005

  6. Ball100 downward D = center-to-center offset Bat 100 upward Undercutting the ball  backspin trajectories NSBP Meeting, February 18, 2005

  7. Fastball: spin reverses Curveball: spin doesn’t reverse   larger for curveball NSBP Meeting, February 18, 2005

  8. In summary….Can a curveball be hit farther than a fastball? • Higher pitch speed  higher hit ball speed on fastball • But…more backspin on curve ball • Net result: curveball goes farther • by a little bit • Mont Hubbard, AJP 71, 1152-1162 (2003) • See also February 2005 issue of AJP for a debate: Hubbard vs. Adair NSBP Meeting, February 18, 2005

  9. Physics Description of Ball-Bat Collision • forces large (>8000 lbs!) • time is short (<1/1000 sec!) • ball compresses, stops, expands • bat compresses ball • ball bends/compresses bat • lots of energy dissipated • distortion of ball • vibrations in bat • ball-bat COR related to energy dissipation • why is aluminum better? Courtesy of CEComposites NSBP Meeting, February 18, 2005

  10. NSBP Meeting, February 18, 2005

  11. Wood versus Aluminum Aluminum has thin shell • Less mass in barrel • easier to swing and control  • but less effective at transferring energy  • Hoop modes • trampoline effect • larger COR  NSBP Meeting, February 18, 2005

  12. The “Trampoline” Effect: A Simple Physical Picture • Two springs mutually compress each other • KE  PE  KE • PE shared between “ball spring” and “bat spring” • PE in ball mostly dissipated(~80%!) • PE in bat mostly restored • Net effect: less overall energy dissipated • ...and therefore higher ball-bat COR • …more “bounce” NSBP Meeting, February 18, 2005

  13. Softball/bat tennis ball/racket strings “Trampoline” Effect NSBP Meeting, February 18, 2005

  14. Experimental Modal Analysis Impact hammer (force transducer) 35 points along length Accelerometer fixed location on barrel FFT Analyzer Frequency Response Function (accel / force) Dan Russell, Kettering U. NSBP Meeting, February 18, 2005

  15. Hoop Modes of Hollow Bats Lowest hoop mode… --that annoying “ping” --“trampoline effect” NSBP Meeting, February 18, 2005

  16. COR correlated with fhoop Energy left in hoop vibrations... Wood bat ~30’ on long fly ball Courtesy of Dan Russell www.kettering.edu/~drussell/bats NSBP Meeting, February 18, 2005

  17. Summary:Why Does Aluminum Outperform Wood? Trampoline effect reduces energy dissipation • More pop • Longer fly ball NSBP Meeting, February 18, 2005

  18. Final Summary • Physics of baseball is a fun application of basic (and not-so-basic) physics • Check out my web site if you want to know more • www.npl.uiuc.edu/~a-nathan/pob • a-nathan@uiuc.edu • Go Red Sox! NSBP Meeting, February 18, 2005

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