"Dead man's float"

[Joel S. Berson]

For buoyancy, back to the classics:

"Any object, wholly or partially immersed in a fluid, is buoyed up by
a force equal to the weight of the fluid displaced by the
object."  Archimedes of Syracuse.

"Archimedes' principle indicates that the upward buoyant force that
is exerted on a body immersed in a fluid, whether fully or partially
submerged, is equal to the weight of the fluid that the body
displaces."  Wikipedia.

The more of ones body that is submerged, the more the water that is
displaced, and the greater the upward force.

Christopher's video below differs only in that the putative diver's
body is bent at the waist.  I don't know what the purpose of that
is.  (He doesn't kick to regain the surface to breathe in, but uses
only his arms.)

Lying horizontal is the survival float upon thin ice -- less weight,
and therefore less pressure, per unit area of the ice.

Joel

At 6/1/2014 09:37 PM, Christopher Philippo wrote:
>On Jun 1, 2014, at 7:38 PM, Spanbock/Svoboda-Spanbock
><spanbocks at VERIZON.NET> wrote:
> > I have a hard time understanding how being vertical could provide
> more buoyancy, since you are distributing the same amount of mass
> over a greater area if you lie horizontally, thereby becoming
> relatively less dense and therefore more buoyant?
>
>"Vertical" is not the best descriptor for the "dead man's
>float"/"jellyfish float":
>https://www.youtube.com/watch?v=JFHClnhrKE8  Arms and legs dangle
>down, not perfectly vertically, and the torso isn't vertical.  I
>don't know if it's the most buoyant position possible - the idea is
>that it's supposed to be an energy-efficient one if you're stranded
>in the water for a long time.

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