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Bing Yu
11-15-2001, 04:55 AM
Dear colleagues,

I need some help to explain some data we obtained in one of our research
project. One of my students did a study on the impact between soccer
ball and head. She used soccer balls in 3 sizes: size 3, size 4, and
size 5. She inflated each ball to 10 PSI, 12 PSI, and 14 PSI, and
measured ball masses. Here are the results:

Size 3 ball: 10 PSI: mass = 0.19947 kg, 12 PSI: mass = 0.20339 kg, 14
PSI: mass = 0.32404 kg

Size 4 ball: 10 PSI: mass = 0.22305 kg, 12 PSI: mass = 0.22309 kg, 14
PSI: mass = 0.36728 kg

Size 5 ball: 10 PSI: mass = 0.25701 kg, 12 PSI: mass = 0.25981 kg, 14
PSI: mass = 0.42660 kg

The student and a biomedical engineering faculty repeatedly measured the
pressures and masses and confirmed these results are correct. Our
questions is: why did ball masses had significant increases when ball
presure increased from 12 PSI to 14 PSI? Thank you very much for your
help.

Bing

--
Bing Yu, Ph.D.
Assistant Professor
Director
Center for Human Movement Science
Division of Physical Therapy
The University of North Carolina at Chapel Hill
Chapel Hill, NC 27599-7135

Tel: 919-843-8643
Fax: 919-966-3678
E-mail: byu@med.unc.edu

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