1 / 21

# Introduction: - PowerPoint PPT Presentation

F M. F d. mg. Introduction: Forces on a Spinning Baseball in Flight. gravity: “physics 101” drag: “wind resistance” lift: Magnus force on spinning baseball. F M. F d. mg. Introduction: Forces on a Spinning Baseball in Flight. drag is opposite to direction of motion

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

## PowerPoint Slideshow about 'Introduction:' - mike_john

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

FM

Fd

mg

Introduction:Forces on a Spinning Baseball in Flight

• gravity: “physics 101”

• drag: “wind resistance”

• lift: Magnus force on spinning baseball

FM

Fd

mg

Introduction:Forces on a Spinning Baseball in Flight

• drag is opposite to direction of motion

• “lift” is in direction that leading edge is turning

• drag effect is huge

• lift effect is smaller but significant

• Reduced distance on fly ball

• Reduction of pitched ball speed by ~10%

• Asymmetric trajectory:

• Total Distance  1.7 x distance at apex

• Optimum home run angle ~350

• Backspin makes ball rise

• “hop” of fastball

• undercut balls: increased distance, reduced optimum angle of home run

• Topspin makes ball drop

• “12-6” curveball

• topped balls nose-dive

• Breaking pitches due to spin

• Cutters, sliders, etc.

Balls hit to left/right curve toward foul pole

Tricky popups with lots of backspin

Let’s Get Quantitative:Measurements of Drag and Lift

• What do we know?

• How do we know it?

• How well do we know it?

• Two types of experiments:

• Wind tunnel

• Measure forces directly

• Video tracking of trajectory

• “You can observe a lot by watching”

• Infer forces from measured acceleration

ATEC 2-wheel pitching machine

Baseball with reflecting dot

Experiment #1: Tracking Trajectory(UC/Davis; Illinois)

Joe Hopkins

Motion Capture Geometry

• Pitching Machine:

• project horizontally

• 50-110 mph

• 1500-4500 rpm

Conclusion: data qualitatively consistent (~20%)

FL= 1/2ACLv2

S=r/v

100 mph, 2000 rpm

S=0.17

FD= 1/2ACDv2

Conclusion:

Major disagreements for v= 70-100 mph

Experiment #2: Sportvision—A Potential New Tool

• Track pitched baseballs with 2 cameras

• High-speed not necessary

• Tracking of MLB game pitches

• Used by ESPN for K-Zone

• From trajectory, determine

• lift,drag,spin axis

• Spin rate not measured

Thanks to Marv White, CTO, for providing a wealth of data

batter’s view

225o

Backspin:

up and in to RHH

batter’s view

135o

Backspin:

up and away to RHH

game pitches

warmup

Uncertainty in drag  50 ft!

• We have much empirical knowledge of lift and drag

• …and some promising new tools for future research

• Things we would like to know better:

• Better data on drag

• “drag crisis”

• Spin-dependent drag?

• Drag for v>100 mph

• Dependence of drag/lift on seam orientation?

• Is the spin constant?