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Author Topic: how much would I weigh if there was no air?  (Read 4816 times)

mcjhn

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how much would I weigh if there was no air?
« on: 08/03/2011 14:33:35 »
how much would i weigh (on earth) if there was no air?

I'm pretty sure you weigh less underwater because of buoyancy? so if the ocean of air was removed would I weigh more, less or the same?

thanks!

p.s. this is assuming your bloodily fluids haven't evaporated etc.

syhprum

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how much would I weigh if there was no air?
« Reply #1 on: 08/03/2011 14:52:26 »
The density of air at normal pressure is about 1/800 that of water the density of our bodies approximates to that of water so the reduction of our weight due to buoyancy is 0.125%.

graham.d

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how much would I weigh if there was no air?
« Reply #2 on: 08/03/2011 15:01:22 »
You get some buoyancy from the air too. Obviously nothing like as much as in water but you are lighter by the weight of the air you displace by the volume of your body. This means that you would be roughly half a kilo heavier if there were no air - depends on your size.

Bored chemist

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how much would I weigh if there was no air?
« Reply #3 on: 08/03/2011 19:15:27 »
If there was no air then the water in your body would boil away. That would reduce your weight a lot.

lightarrow

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how much would I weigh if there was no air?
« Reply #4 on: 08/03/2011 19:30:26 »
"how much would I weigh if there was no air?"

The same. Weigh is m*g and mass is the same, gravity is the same.

Vereava

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how much would I weigh if there was no air?
« Reply #5 on: 08/03/2011 22:45:02 »
"how much would I weigh if there was no air?"

The same. Weigh is m*g and mass is the same, gravity is the same.

But if there's no air, then you would remove the mass of the air in your body, right? So this would mean that technically you weigh less... but then you can't breathe so I guess you won't be able to see your weight

The real question here should be "What would the scale say in a vacuum?"
« Last Edit: 08/03/2011 22:47:07 by Vereava »

Geezer

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how much would I weigh if there was no air?
« Reply #6 on: 09/03/2011 01:29:45 »
The same. Weigh is m*g and mass is the same, gravity is the same.

There seem to be different schools of thought about that. Some definitions say it's how much you actually weigh (on some sort of weighing device). If so, your weight varies with changes in atmospheric pressure.

Probably a good reason to stick with "mass"

lightarrow

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how much would I weigh if there was no air?
« Reply #7 on: 09/03/2011 15:13:35 »
The same. Weigh is m*g and mass is the same, gravity is the same.

There seem to be different schools of thought about that. Some definitions say it's how much you actually weigh (on some sort of weighing device). If so, your weight varies with changes in atmospheric pressure.

Probably a good reason to stick with "mass"
No only with atm pressure, but with density too. Physicists don't measure a balloon's mass with a balance...

lightarrow

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how much would I weigh if there was no air?
« Reply #8 on: 09/03/2011 15:19:29 »
But if there's no air, then you would remove the mass of the air in your body, right?
Astronauts don't go around in space without a spacesuit, for what I know
(It's only a joke, no one talked of astronauts in space, of course, it's the question that it's not well defined).
Quote
The real question here should be "What would the scale say in a vacuum?"
It would be a better question, indeed, but we should ask the OP if this is what he actually intended.

syhprum

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how much would I weigh if there was no air?
« Reply #9 on: 09/03/2011 16:19:39 »
I think that if you were immersed in one of the heavier gases such as xenon in a highly compressed form you would have enough buoyancy to float.
Radon would require less pressure but is not good to breath!
« Last Edit: 09/03/2011 16:26:28 by syhprum »

graham.d

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how much would I weigh if there was no air?
« Reply #10 on: 09/03/2011 16:29:24 »
I see no confusion or ambiguity in the question at all. The question cited the buoyancy of water which would make a person weigh less and asked if air would have a similar effect (even if much less). In the spirit the question was asked, the answer is "yes". Clearly the questioner was weighing as measuring the net downward force on scales. Good grief!

I have a question regarding angels and pin heads but I will refrain from asking :-)

Geezer

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how much would I weigh if there was no air?
« Reply #11 on: 09/03/2011 18:29:00 »
I have a question regarding angels and pin heads but I will refrain from asking :-)

Too late Graham. Syhprum already did that one

lightarrow

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how much would I weigh if there was no air?
« Reply #12 on: 09/03/2011 21:27:12 »
I see no confusion or ambiguity in the question at all. The question cited the buoyancy of water which would make a person weigh less and asked if air would have a similar effect (even if much less).
Yes, I was too tired when I wrote that...

Soul Surfer

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how much would I weigh if there was no air?
« Reply #13 on: 09/03/2011 23:09:19 »
The effective buoyancy caused by air has to be allowed for if you are weighing things very accurately.  My old book of physical constants has a nomogram to help you correct the weight of any object measured using a balance  in air to the correct value as measured in a vacuum.  This depends on the density of the thing that you are weighing  and the density of the weights you are using.  clearly if both densities are the same there is no correction.  The range of correction can be up to plus or minus one part in one thousand

imatfaal

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how much would I weigh if there was no air?
« Reply #14 on: 10/03/2011 11:56:50 »
S-Surfer thanks - had to look up nomogram, really interesting.  Fascinating and beautiful diagrams, so much so that I might seek one out with relevance to my industry for the office wall

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how much would I weigh if there was no air?
« Reply #14 on: 10/03/2011 11:56:50 »