Michael...you are indeed correct. I think the problem here is that the
scientific definition of buoyancy is the positive component, while the
common diving definition is really the resultant weight. A increase in
resultant weight is what he was after....

Anyways... I think we all agree there is no good reason to modify the light
like this.

I guess I've been doing more diving than physics.  ;-)

Drew

> No, It is absolutely correct.
>
> Buoyancy is the force imposed on an object by the surrounding medium.  It
> is frequently stated as: "an object is buoyed up by a force equal to the
> weight of the medium displaced by the object".  This is a function solely
> of the volume of the object and the density of the fluid.  The density (or
> weight) of the object is not a factor.
>
> What you are thinking of is the resultant weight.  This is result of
adding
> two forces: buoyancy (usually with a negative sign) and gravity.  The
> original poster was not looking to add weight, he was looking to reduce
the
> buoyant force of the canister, and hence reduce the total weight he had to
> carry.  This cannot be done be reducing the air space inside a rigid
> canister (because the density of the object doesn't affect the buoyancy)
> but only by reducing the volume.
>
> He could reduce the buoyancy by, say, filing half the thickness off the
> outer side of the canister (not recommended), but not by filling in the
> airspace inside.
>
> mike
>
> At 10:57 PM 6/1/00 -0400, Drew Glasbrenner wrote:
> >This is wrong.
> >
> >  Buoyancy is the weight of an object minus the weight of the volume of
water
> >it displaces. This is why a canister with batteries is negatively
buoyant,
> >and a canister with air or anything that weighs less than the amount of
> >displaced water is positively buoyant. If he adds lead to the inside of
the
> >canister, it will make it more negatively buoyant.
> >
> >Drew Glasbrenner
> >
> > > The canister has a fixed amount of buoyancy as a result of its
> > > displacement. FIlling it with feathers, epoxy or lead will not effect
> >that.
> > > You can make it heavier or lighter, but that displacement and
resulting
> > > buoyancy will always be the same.
> >
> >--
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>

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