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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