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Falling Cats: using physics to resolve an apparent
biological paradox
http://www.flickr.com/photos/nebarnix/322854875/Some rights reserved: http://creativecommons.org/licenses/by-nc-nd/2.0/
© J. A. Bolker and D. C. Meredith, UNH, 2009
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Cats who fall >7 stories survive…
• Better than humans who fall the same distance;
and• Better than cats falling <7 stories!
WHY?
Diamond, J. 1989. How cats survive falls from New York skyscrapers. Natural History 98:20-26
Data are based on veterinary records of accidental falls - not deliberate defenestration of felines.
© J. A. Bolker and D. C. Meredith, UNH, 2009
© J. A. Bolker and D. C. Meredith, UNH, 2009
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Effect of pressure drag
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free fall cat human
© J. A. Bolker and D. C. Meredith, UNH, 2009
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Explanation = physics:
• How hard you hit depends on how fast you are going…which depends on
• (a) your mass, and g;• (b) how long you have been accelerating and• (c) your maximum possible falling speed (a.k.a. terminal velocity).• terminal velocity is lower for cats; they reach it sooner; and once
they do, they adjust their behavior.
Effect of pressure drag
0
20
40
60
80
100
120
140
160
0 200 400 600 800 1000
x(m)
v(m/s)
free fall cat human
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