"Dead man's float"

[Spanbock/Svoboda-Spanbock]

But if you drop a toothpick into a bowl of water point down, it will rise to a horizontal position, i.e. presumably the most naturally efficient position for floatation, which I presume is what we mean by most buoyant. It will also stay horizontal if you drop it in horizontally. I just tested it, to be sure that I wasn't crazy.

It has been more than 25 years since I studied Archimedes, but, I think there must be some problem in equating the magnitude of the force involved with buoyancy?

--
Kate




On Jun 2, 2014, at 9:29 AM, Joel S. Berson wrote:

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> Sender:       American Dialect Society <ADS-L at LISTSERV.UGA.EDU>
> Poster:       "Joel S. Berson" <Berson at ATT.NET>
> Subject:      Re: "Dead man's float"
> -------------------------------------------------------------------------------
>
> 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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