The classic experiment to measure the drag coefficient involves dropping coffee filters.1 Wouldn't it be more fun to try something different? In fact, an experiment on the drag force is conducted nearly 4000 times a day during the baseball season and you have free access to this PITCHf/x data!2
REFERENCES
2.
For instructions to get to and use the PITCHf/x data set, see
D. T.
Kagan
, “The anatomy of a pitch: Doing physics with PITCHf/x data
,” Phys. Teach.
47
(7
), 412
(Oct. 2009
).3.
The drag coefficient is known to be a function of the speed. Since most professionally pitched baseballs are thrown within the narrow range of 70 to 100 mph, we'll neglect this complication here. See http://www.grc.nasa.gov/WWW/k-12/airplane/balldrag.html.
4.
Official Baseball Rules
(2013
ed.), Rule 1.09.5.
No apologies! The traditions of the national pastime give it an exemption from the constraints of the SI system. If the units bother you, then the fact that the PITCHf/x system has a serious significant figure problem will send you into orbit.
6.
An online calculator that assumes standard pressure can be found at http://www.denysschen.com/catalogue/density.aspx. A formula that omits elevation can be found at “
Density of Moist Air
,” in CRC Handbook of Chemistry and Physics
, 63rd ed., edited by David R.
Lide
(CRC Press
, Boca Raton, FL
, 2005
). There is a spreadsheet available at http://baseball.phys-ics.illinois.edu/trajectory-calculator.html that will calculate the density of air and use it to predict the trajectory of a pitched or hit ball.7.
Game time temperature can be found in the box score at http://MLB.com.
8.
The local humidity can be found at http://www.wunderground.com/history/ as can other historical weather data.
9.
Historical pressure data can be found at http://trexwww.ucc.nau.edu/cgi-bin/daily_average.pl?user_param=64101.
10.
The ball park elevations can be found at http://baseballjudgments.tripod.com/id62.html.
12.
For a complete and thorough discussion of the forces on a baseball in flight, see
A. M.
Nathan
, “The effect of spin on the flight of a baseball
,” Am. J. Phys.
76
, 119
–124
(2008
).13.
Comparing calculated versus measured values for the drag coefficient can be used as a test of the PITCHf/x system. See http://baseball.physics.illinois.edu/LiftDrag-1.pdf.
14.
R. K.
Adair
, The Physics of Baseball
, 3rd ed. (Harper & Row, Publishers Inc.
, New York
, 2002
), p. 8
, Fig. 2.1.15.
See the graph in the link of Ref. 13.
© 2014 American Association of Physics Teachers.
2014
American Association of Physics Teachers
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