Re: [Phys-L] sports physics

[John Denker <jsd@av8n.com>]

On 09/19/2013 03:46 PM, Anthony Lapinski wrote:
 
> yahoo.com/blogs/mlb-big-league-stew/marlins-adeiny-hechavarria-makes-incredible-jump-snag-liner-180906842--mlb.html

The following URL works better:

http://sports.yahoo.com/blogs/mlb-big-league-stew/marlins-adeiny-hechavarria-makes-incredible-jump-snag-liner-180906842--mlb.html

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> Good physics -- the leap is very high! Now check the slo-mo replay around
> 33 s. The guy twists his body around to land face down. It reminded me of
> videos showing a cat dropped upside down. The cats twists to land feet
> first.

The audio from the common taters is misleading.  It suggests he
was trying to land feet first but was "not able to do that".

Understanding the physics starts from realizing that "feet first"
and "face first" are not the only possibilities.  Among the many
possibilities, in reverse order of preference, are
   back-of-head first << face first << feet first

As I see it, the point is that the geometry of the jump plus
the angular momentum of the ball would naturally lead to a
possible supine landing, which would be a very bad thing.
Landing prone is not nearly so bad, because it allows using 
the arms to break the fall.  Landing feet first would of 
course be better, because it means falling not so far, and 
allows using the legs to break the fall, but this was not
an available option in this case.

As another point of physics, note that you can flip quicker
around the long axis than around either of the other two
axes, because of the much lower moment of inertia.

So, as is so often the case, the athlete knew what he was
doing, even if the taters didn't know how to explain it.