

Calculating Speed of Antelope in an image - ruchi
http://www.reddit.com/r/pics/comments/b60hs/jesus_antelope/c0l5ujt?context=3

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gjm11
A nice back-of-envelope calculation. Someone posted a picture showing an
antelope running through shallow water. Someone else realised that you can use
just that single picture to estimate how fast the antelope is moving. The
clever bit is estimating the speed of the water waves you can see spreading
out from places where the antelope touched down.

However, I am unconvinced by some details. For instance, I think s/he
overestimated the amount of water wave movement by maybe a factor of 2, the
wavelength looks way too large too, and I suspect the water is deeper than
s/he assumed. My estimate of the antelope's speed is more like 40mph, which is
still very impressive given that it's running through water.

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pyre
Why do you suppose that the water is deeper than 1 ft?

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bprater
If it were much deeper, I'm not sure the animal could have sustained it's
velocity. I cannot walk normally in six inches of ocean water.

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mnemonicsloth
Yes, but you're (presumably) _h. sapiens._ You've got big flat feet that
displace a lot of water (twice) every time you take a step.

An antelope's hooves are hard and narrow, so they generate less turbulence
going into the water. I'm not sure how the antelope deals with the mud on the
bottom of the river, though.

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cfpg
Deer hooves open forming a V shape when touching the floor, that's how they
don't get stuck when drinking water from a lake. I would guess speed is also
important.

