The topic is summarised nicely by
J.B.S. Haldane in his essay
On Being the Right Size
You can drop a mouse
down a thousand-yard mine shaft; and, on arriving at the bottom,
it gets a slight shock and walks away, provided that the ground is
fairly soft. A rat is killed, a man is broken, a
horse splashes.
This assertion
depends on air resistance.
Drag acts against the force of gravity
on a falling object; the object reaches terminal
velocity when the force of gravity is equal to
the drag. Obviously the smaller the terminal velocity,
the better the chance of a happy landing. Very roughly
the terminal velocity is proportional to the size of the falling object.
So the terminal velocity of
a mouse is approximately 1% of that of an elephant.
To give specific examples, a parachutist
falls gently to earth at around 5 m/s
whereas a bacterium is travelling at
2.8 x 10-4 m/s.
In a study done by some New York city vets
(where apparently it is quite common for cats
to be defenestrated) it was found that
it takes a cat about 7 floors to hit
terminal velocity and that a cat can often survive this
with nothing worse than a nosebleed.
Some facts were sourced from
-
http://www.pls.lib.ca.us/smcccd/faculty/goth/MainPages/Scaling/Scaling.htm
-
the rats-digest mailing list at the University of Washington,
-
http://ffden-2.phys.uaf.edu/211.web.stuff/Kuhns/variables.htm,
and
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http://members.aol.com/gunghey/archivedpageupdates.html.