Archimedes wrote: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.
Krikkit_Robot wrote:You do not become more buoyant by having a lung full of air.
Yes your volume increases but so does your overall weight.
I just think of a balloon under water. An empty balloon (with no inside volume) will be as buoyant as as a balloon filled to capacity with water. But if you put more water in the balloon to the point where the rubber starts to stretch the water inside is slightly compressed and becomes slightly (very slightly) more dense and less botany.
Kobayashi_Maru wrote:Interesting point! According to Wikipedia: the atmosphere is about 21% oxygen, about 5% of the air we breathe out is CO2 (which was O2 when we breathed it in), we breathe in about 500mL in a normal breathe, and an average adult breathes 12-20 times per minute.
Now, applying the Ideal Gas Law at STP gives us: PV/RT = n = 0.0208 moles of air per breath, or 0.0044 moles of O2 (in) and C02 (out) per breath. So we lose ~.052g of carbon per breath, which amounts to 38-63 grams of carbon per hour, or 0.9-1.5 kg of carbon per day.
That seems high by at least an order of magnitude. There's no way we breath out that much carbon a day. Have I made a mistake in my figures, or are the input values from Wikipedia just BS? Can I get some corroboration?
jareds wrote:You use the atmospheric oxygen content, 21%, to go from 0.0208 moles to 0.0044 moles, although you earlier state we exhale 5% carbon dioxide. The oxygen content is irrelevant since we don't metabolize 100% of what we inhale. So, if we use your input values that actual result will be about 1/4 of the one you gave. I have no particular expertise to know whether the input values are correct.
gmalivuk wrote:Why do you think that seems an order of magnitude too high?
gmalivuk wrote:Do you weigh your poop? The reason I was skeptical was because I really don't know what my personal experience would tell me about how much weight I exhale daily, compared to how much I excrete in liquid or solid form and compared to how much I eat and drink.
yusri106 wrote:The mass of air you inhaled or exhaled is actually really small and can be neglected, so the mass changes is negligible
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