Boyancy and Gravity! [Archive]

Gremlin

Nov14-04, 11:59 AM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\nThe average atmospheric pressure at Earth\'s surface is about 14.6 pounds\nper square inch, which is about 100,000 pascals.\n\nWhat would gravity on the earth be like without this air pressure, with 0\npascals of air pressure? If you look at a helium balloon it obviously has\nmass, yes.. but it has no actual weight.. if you were to measure it on a\nscale. So obviously air pressure factors in to somethings weight. My\nquestion is how much would an average person weigh if it were not for air\npressure? Or in general any discussion about the topic.\n\nApparently the force of gravity keeps air around the earth. Perhaps though\nthe air is just more dense than the near vacuum of space so it collects\nitself into on place. That is my theory, as what gravity actually is..\nJust an effect of buoyancy. No need to argue with me about it because I\ndon\'t have any evidence to support my idea.. yet. Solids also collect\nthemselves because of buoyancy in near vacuum and in air.. As does water\netc. This is why a rock will sink in water, and water will sink in air..\nand helium will rise in air. Everything though will sink in the near\nvacuum of space though because buoyancy is caused by density and vacuum is\nthe least dense of everything. It is just there is no \'down\' for anything\nto sink in, in vacuum so everything just collects together and creates a\ndown consistent with that collection of matter.\n\nWhat do you think!?\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>The average atmospheric pressure at Earth's surface is about 14.6 pounds
per square inch, which is about 100,000 pascals.

What would gravity on the earth be like without this air pressure, with
pascals of air pressure? If you look at a helium balloon it obviously has
mass, yes.. but it has no actual weight.. if you were to measure it on a
scale. So obviously air pressure factors in to somethings weight. My
question is how much would an average person weigh if it were not for air
pressure? Or in general any discussion about the topic.

Apparently the force of gravity keeps air around the earth. Perhaps though
the air is just more dense than the near vacuum of space so it collects
itself into on place. That is my theory, as what gravity actually is..
Just an effect of buoyancy. No need to argue with me about it because I
don't have any evidence to support my idea.. yet. Solids also collect
themselves because of buoyancy in near vacuum and in air.. As does water
etc. This is why a rock will sink in water, and water will sink in air..
and helium will rise in air. Everything though will sink in the near
vacuum of space though because buoyancy is caused by density and vacuum is
the least dense of everything. It is just there is no 'down' for anything
to sink in, in vacuum so everything just collects together and creates a
down consistent with that collection of matter.

What do you think!?

chris h fleming

Nov16-04, 02:56 AM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\nGremlin <virtualadepts.nospam@gmail.com> wrote in message news:<Xns95A16F8E95E93Test@216.168.3.44>...\n> The average atmospheric pressure at Earth\'s surface is about 14.6 pounds\n> per square inch, which is about 100,000 pascals.\n>\n> What would gravity on the earth be like without this air pressure, with 0\n> pascals of air pressure?\n\nIf there were no atmosphere? By Gauss\'s law the atmosphere contributes\nno gravitational force to us on the earth, but only to those in the\natmosphere or in outerspace. The difference felt by a space traveler\nwould depend on how much mass is in the atmosphere.\n\n> If you look at a helium balloon it obviously has\n> mass, yes.. but it has no actual weight..\n\nI believe the balloon certainly does have weight. Try weighing it in a\nvacuum. The balloon is just less dense than air, so it floats in air.\nOn the moon it would drop.\n\n> if you were to measure it on a\n> scale. So obviously air pressure factors in to somethings weight.\n\nGravity gives us weight that pushes us down. Air gives us buoyancy\nthat pushes us up. You seem to be saying that weight = gravity +\nbuoyancy. That is what is measured on a scale, but to a scientist\nweight = gravity only.\n\n> My\n> question is how much would an average person weigh if it were not for air\n> pressure? Or in general any discussion about the topic.\n\nThe scale would measure less the force of buoyancy. Which is just the\nweight of a person sized amount of air.\nSo take a person as about 1/2 meter x 1/2 meter x 2 meters = 1/2\nmeter^3 volume.\nAnd the density of air being 1.29 kilograms/meter^3.\nA person sized amount of air would have a mass of about .6 kilograms\nand what ever that would translate to in pounds on earth\'s surface\n\nso that\'s the difference.\n\n> Apparently the force of gravity keeps air around the earth.\n\nApparently\n\n> Perhaps though\n> the air is just more dense than the near vacuum of space so it collects\n> itself into on place. That is my theory, as what gravity actually is..\n> Just an effect of buoyancy. No need to argue with me about it because I\n> don\'t have any evidence to support my idea.. yet. Solids also collect\n> themselves because of buoyancy in near vacuum and in air.. As does water\n> etc. This is why a rock will sink in water, and water will sink in air..\n> and helium will rise in air. Everything though will sink in the near\n> vacuum of space though because buoyancy is caused by density and vacuum is\n> the least dense of everything. It is just there is no \'down\' for anything\n> to sink in, in vacuum so everything just collects together and creates a\n> down consistent with that collection of matter.\n>\n> What do you think!?\n\nI think there is one simple thought experiment that proves this theory\nwrong.\n\nWhat happens when you open the door of a space shuttle (while in outer\nspace)? By your theory the air would stay in the ship because of\nvacuum buoyancy. But the air will diffuse into outerspace! And you\nprobably know this.\n\nIf you are interested in these ideas, then you should study Newtonian\ngravity, buoyancy, pressure, and diffusion.\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>Gremlin <virtualadepts.nospam@gmail.com> wrote in message news:<Xns95A16F8E95E93Test@216.168.3.44>...
> The average atmospheric pressure at Earth's surface is about 14.6 pounds
> per square inch, which is about 100,000 pascals.
>
> What would gravity on the earth be like without this air pressure, with
> pascals of air pressure?

If there were no atmosphere? By Gauss's law the atmosphere contributes
no gravitational force to us on the earth, but only to those in the
atmosphere or in outerspace. The difference felt by a space traveler
would depend on how much mass is in the atmosphere.

> If you look at a helium balloon it obviously has
> mass, yes.. but it has no actual weight..

I believe the balloon certainly does have weight. Try weighing it in a
vacuum. The balloon is just less dense than air, so it floats in air.
On the moon it would drop.

> if you were to measure it on a
> scale. So obviously air pressure factors in to somethings weight.

Gravity gives us weight that pushes us down. Air gives us buoyancy
that pushes us up. You seem to be saying that weight = gravity +
buoyancy. That is what is measured on a scale, but to a scientist
weight = gravity only.

> My
> question is how much would an average person weigh if it were not for air
> pressure? Or in general any discussion about the topic.

The scale would measure less the force of buoyancy. Which is just the
weight of a person sized amount of air.
So take a person as about 1/2 meter x 1/2 meter x 2 meters = 1/2meter^3 volume.
And the density of air being 1.29 kilograms/meter^3.
A person sized amount of air would have a mass of about .6 kilograms
and what ever that would translate to in pounds on earth's surface

so that's the difference.

> Apparently the force of gravity keeps air around the earth.

Apparently

> Perhaps though
> the air is just more dense than the near vacuum of space so it collects
> itself into on place. That is my theory, as what gravity actually is..
> Just an effect of buoyancy. No need to argue with me about it because I
> don't have any evidence to support my idea.. yet. Solids also collect
> themselves because of buoyancy in near vacuum and in air.. As does water
> etc. This is why a rock will sink in water, and water will sink in air..
> and helium will rise in air. Everything though will sink in the near
> vacuum of space though because buoyancy is caused by density and vacuum is
> the least dense of everything. It is just there is no 'down' for anything
> to sink in, in vacuum so everything just collects together and creates a
> down consistent with that collection of matter.
>
> What do you think!?

I think there is one simple thought experiment that proves this theory
wrong.

What happens when you open the door of a space shuttle (while in outer
space)? By your theory the air would stay in the ship because of
vacuum buoyancy. But the air will diffuse into outerspace! And you
probably know this.

If you are interested in these ideas, then you should study Newtonian
gravity, buoyancy, pressure, and diffusion.

Doug Sweetser

Nov16-04, 02:56 AM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\nHello Gremlin:\n\nThe air makes no erect on people\'s weight due to the air. Zippo.\nNewton proved this one, but took him 20 years to figure out the proof.\n\nThink of the atmosphere as a series of shells. We are inside those\nshells. Newton was able to show that inside a hollow shell, there is\nno gravity field. See you are attracted to the near side shell. And\nyou are attracted to the far side of the shell. The area of the shell\ninvolved is smaller for the near side. Because gravity is exactly an\ninverse square law, those two effects exactly cancel.\n\nExperimentalists have looked carefully for any deviation from an inverse\nsquare law. So far none has been found in the lab.\n\nGravity is not about buoyancy.\n\ndoug\nquaternions.com\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>Hello Gremlin:

The air makes no erect on people's weight due to the air. Zippo.
Newton proved this one, but took him 20 years to figure out the proof.

Think of the atmosphere as a series of shells. We are inside those
shells. Newton was able to show that inside a hollow shell, there is
no gravity field. See you are attracted to the near side shell. And
you are attracted to the far side of the shell. The area of the shell
involved is smaller for the near side. Because gravity is exactly an
inverse square law, those two effects exactly cancel.

Experimentalists have looked carefully for any deviation from an inverse
square law. So far none has been found in the lab.

Gravity is not about buoyancy.

doug
quaternions.com

CWatters

Nov16-04, 02:56 AM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\n"Gremlin" <virtualadepts.nospam@gmail.com> wrote in message\nnews:Xns95A16F8E95E93Test@216.168.3.44... \n>\n>\n> The average atmospheric pressure at Earth\'s surface is about 14.6 pounds\n> per square inch, which is about 100,000 pascals.\n>\n> What would gravity on the earth be like without this air pressure, with 0\n> pascals of air pressure? If you look at a helium balloon it obviously has\n> mass, yes.. but it has no actual weight.. if you were to measure it on a\n> scale. So obviously air pressure factors in to somethings weight. My\n> question is how much would an average person weigh if it were not for air\n> pressure? Or in general any discussion about the topic.\n\nhttp://www.centennialofflight.gov/essay/Dictionary/buoyancy/DI13.htm\n\nQuote: Buoyancy is a physical law that was discovered by the Greek\nmathematician and inventor Archimedes in the third century BC. The\nprinciple, called Archimedes\' principle, states that any body floating or\nsubmerged in a fluid (gas or liquid) is buoyed upward by a force equal to\nthe weight of the displaced fluid. Balloons rise because the air pressure\nacting upward against it is greater than the pressure above that is pushing\ndownward. The buoyancy is numerically equal to the weight of the fluid (air\nin the case of a balloon) displaced. An object surrounded by air (like a\nballoon) is buoyed upward by a force equal to the weight of the air\ndisplaced. If the mass of the object is less than the weight of an equal\nvolume of air, the object rises. If the weight of the object is greater than\nthe mass of an equal volume of air, it falls."\n\n\nSo a person who displaces an amount x of air would weigh x more if the air\nwas removed.\n\nColin\n\nAside: While looking for a good reference site I also found this one:\n\nhttp://www.nasm.si.edu/exhibitions/gal109/NEWHTF/HTF310.HTM\n\nIt appears to be wrong or have I made a mistake?. The shape of the balloon\nshouldn\'t matter should it? I mean within limits a short flat Balloon and a\ntall thin one (of equal volume) should displace the same volume and have the\nsame bouyancy.\n\n\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>"Gremlin" <virtualadepts.nospam@gmail.com> wrote in message
news:Xns95A16F8E95E93Test@216.168.3.44...
>
>
> The average atmospheric pressure at Earth's surface is about 14.6 pounds
> per square inch, which is about 100,000 pascals.
>
> What would gravity on the earth be like without this air pressure, with
> pascals of air pressure? If you look at a helium balloon it obviously has
> mass, yes.. but it has no actual weight.. if you were to measure it on a
> scale. So obviously air pressure factors in to somethings weight. My
> question is how much would an average person weigh if it were not for air
> pressure? Or in general any discussion about the topic.

http://www.centennialofflight.gov/essay/Dictionary/buoyancy/DI13.htm

Quote: Buoyancy is a physical law that was discovered by the Greek
mathematician and inventor Archimedes in the third century BC. The
principle, called Archimedes' principle, states that any body floating or
submerged in a fluid (gas or liquid) is buoyed upward by a force equal to
the weight of the displaced fluid. Balloons rise because the air pressure
acting upward against it is greater than the pressure above that is pushing
downward. The buoyancy is numerically equal to the weight of the fluid (air
in the case of a balloon) displaced. An object surrounded by air (like a
balloon) is buoyed upward by a force equal to the weight of the air
displaced. If the mass of the object is less than the weight of an equal
volume of air, the object rises. If the weight of the object is greater than
the mass of an equal volume of air, it falls."

So a person who displaces an amount x of air would weigh x more if the air
was removed.

Colin

Aside: While looking for a good reference site I also found this one:

http://www.nasm.si.edu/exhibitions/gal109/NEWHTF/HTF310.HTM

It appears to be wrong or have I made a mistake?. The shape of the balloon
shouldn't matter should it? I mean within limits a short flat Balloon and a
tall thin one (of equal volume) should displace the same volume and have the
same bouyancy.

John T Lowry

Nov16-04, 02:56 AM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\n"Gremlin" <virtualadepts.nospam@gmail.com> wrote in message\nnews:Xns95A16F8E95E93Test@216.168.3.44... \n>\n>\n> The average atmospheric pressure at Earth\'s surface is about 14.6\n> pounds\n> per square inch, which is about 100,000 pascals.\n>\n> What would gravity on the earth be like without this air pressure,\n> with 0\n> pascals of air pressure? If you look at a helium balloon it obviously\n> has\n> mass, yes.. but it has no actual weight.. if you were to measure it on\n> a\n> scale. So obviously air pressure factors in to somethings weight. My\n> question is how much would an average person weigh if it were not for\n> air\n> pressure? Or in general any discussion about the topic.\n>\n> Apparently the force of gravity keeps air around the earth. Perhaps\n> though\n> the air is just more dense than the near vacuum of space so it\n> collects\n> itself into on place. That is my theory, as what gravity actually\n> is..\n> Just an effect of buoyancy. No need to argue with me about it because\n> I\n> don\'t have any evidence to support my idea.. yet. Solids also collect\n> themselves because of buoyancy in near vacuum and in air.. As does\n> water\n> etc. This is why a rock will sink in water, and water will sink in\n> air..\n> and helium will rise in air. Everything though will sink in the near\n> vacuum of space though because buoyancy is caused by density and\n> vacuum is\n> the least dense of everything. It is just there is no \'down\' for\n> anything\n> to sink in, in vacuum so everything just collects together and creates\n> a\n> down consistent with that collection of matter.\n>\n> What do you think!?\n\nYou need to read about buoyancy, to find out what it is and how it\nworks. It is true that we weigh somewhat less than we would in a vacuum\n(by the weight of an equal volume of air at our location), but buoyancy\nwill not explain gravity in any way shape or form.\n\nJohn Lowry\nFlight Physics\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>"Gremlin" <virtualadepts.nospam@gmail.com> wrote in message
news:Xns95A16F8E95E93Test@216.168.3.44...
>
>
> The average atmospheric pressure at Earth's surface is about 14.6
> pounds
> per square inch, which is about 100,000 pascals.
>
> What would gravity on the earth be like without this air pressure,
> with
> pascals of air pressure? If you look at a helium balloon it obviously
> has
> mass, yes.. but it has no actual weight.. if you were to measure it on
> a
> scale. So obviously air pressure factors in to somethings weight. My
> question is how much would an average person weigh if it were not for
> air
> pressure? Or in general any discussion about the topic.
>
> Apparently the force of gravity keeps air around the earth. Perhaps
> though
> the air is just more dense than the near vacuum of space so it
> collects
> itself into on place. That is my theory, as what gravity actually
> is..
> Just an effect of buoyancy. No need to argue with me about it because
> I
> don't have any evidence to support my idea.. yet. Solids also collect
> themselves because of buoyancy in near vacuum and in air.. As does
> water
> etc. This is why a rock will sink in water, and water will sink in
> air..
> and helium will rise in air. Everything though will sink in the near
> vacuum of space though because buoyancy is caused by density and
> vacuum is
> the least dense of everything. It is just there is no 'down' for
> anything
> to sink in, in vacuum so everything just collects together and creates
> a
> down consistent with that collection of matter.
>
> What do you think!?

You need to read about buoyancy, to find out what it is and how it
works. It is true that we weigh somewhat less than we would in a vacuum
(by the weight of an equal volume of air at our location), but buoyancy
will not explain gravity in any way shape or form.

John Lowry
Flight Physics

Richard Saam

Nov16-04, 02:59 AM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\nGremlin wrote:\n\n>The average atmospheric pressure at Earth\'s surface is about 14.6 pounds\n>per square inch, which is about 100,000 pascals.\n>\n>What would gravity on the earth be like without this air pressure, with 0\n>pascals of air pressure? If you look at a helium balloon it obviously has\n>mass, yes.. but it has no actual weight.. if you were to measure it on a\n>scale. So obviously air pressure factors in to somethings weight. My\n>question is how much would an average person weigh if it were not for air\n>pressure? Or in general any discussion about the topic.\n>\n>\nFrom any general text in fluid mechanics:\n\nspecific weight of water is 62.4 lb/ft^3\nspecific weight of air is .08 lb/ft^3\n\nAssuming person\'s specific weight (lb/ft^3) can be approximated by\nspecific weight of water, then that person with a given volume (V ft^3)\nwill weigh in air:\n\n(62.4 - .08) x V lb\n\nAssuming person in a vacuum, the his/her weight would be:\n\n(62.4) x V lb\n\nRichard Saam\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>Gremlin wrote:

>The average atmospheric pressure at Earth's surface is about 14.6 pounds
>per square inch, which is about 100,000 pascals.
>
>What would gravity on the earth be like without this air pressure, with
>pascals of air pressure? If you look at a helium balloon it obviously has
>mass, yes.. but it has no actual weight.. if you were to measure it on a
>scale. So obviously air pressure factors in to somethings weight. My
>question is how much would an average person weigh if it were not for air
>pressure? Or in general any discussion about the topic.
>
>
From any general text in fluid mechanics:

specific weight of water is 62.4 lb/ft^3
specific weight of air is .08 lb/ft^3

Assuming person's specific weight (lb/ft^3) can be approximated by
specific weight of water, then that person with a given volume (V ft^3)
will weigh in air:

(62.4 - .08) x V lb

Assuming person in a vacuum, the his/her weight would be:

(62.4) x V lb

Richard Saam

Ralph Hartley

Nov17-04, 10:46 AM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>chris h fleming wrote:\n\n> The scale would measure less the force of buoyancy. Which is just the\n> weight of a person sized amount of air.\n> So take a person as about 1/2 meter x 1/2 meter x 2 meters = 1/2\n> meter^3 volume.\n\nYikes!\n\nPeople just barely float, they have about the same density as water. A\nperson who displaces 1/2 meter^3 would weigh about 500kg. Half a ton!\n\nI know that the developed world is suffering an epidemic of obesity, but I\ndon\'t think it\'s *that* bad yet.:-)\n\n> And the density of air being 1.29 kilograms/meter^3.\n> A person sized amount of air would have a mass of about .6 kilograms\n> and what ever that would translate to in pounds on earth\'s surface\n\nA (more healty:-)) 70kg person has a volume of ~70 liters or 0.07 m^3, and\nwould displace 0.07*1.29 = 0.09 Kg. So buoyancy reduces a typical person\'s\napparent weight by 90 grams, or about three ounces.\n\nAnother way of looking at it is that buoyancy is about 1.29/1000 = 0.129%\nof a person\'s weight.\n\nRalph Hartley\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>chris h fleming wrote:

> The scale would measure less the force of buoyancy. Which is just the
> weight of a person sized amount of air.
> So take a person as about 1/2 meter x 1/2 meter x 2 meters = 1/2
> meter^3 volume.

Yikes!

People just barely float, they have about the same density as water. A
person who displaces 1/2 meter^3 would weigh about 500kg. Half a ton!

I know that the developed world is suffering an epidemic of obesity, but I
don't think it's *that* bad yet.:-)

> And the density of air being 1.29 kilograms/meter^3.
> A person sized amount of air would have a mass of about .6 kilograms
> and what ever that would translate to in pounds on earth's surface

A (more healty:-)) 70kg person has a volume of ~70 liters or .07 m^3, and
would displace .07*1.29 = .09 Kg. So buoyancy reduces a typical person's
apparent weight by 90 grams, or about three ounces.

Another way of looking at it is that buoyancy is about 1.29/1000 = .129%
of a person's weight.

Ralph Hartley

Peter

Nov17-04, 10:50 AM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>chris h fleming wrote:\n>>My\n>>question is how much would an average person weigh if it were not for air\n>>pressure? Or in general any discussion about the topic.\n>\n>\n> The scale would measure less the force of buoyancy. Which is just the\n> weight of a person sized amount of air.\n> So take a person as about 1/2 meter x 1/2 meter x 2 meters = 1/2\n> meter^3 volume.\n> And the density of air being 1.29 kilograms/meter^3.\n> A person sized amount of air would have a mass of about .6 kilograms\n\nThat\'s a very large person. Most people have a density just about\nequal to water (i.e. if I have my lungs full of air I float but when I\nexhale I sink). 0.5 cubic meters at that density has a mass of\n500 kg or weight of about 1100 lbs.\n\nA more reasonable volume would be based on a weight of about 160 lbs\nwhich corresponds to a volume of 0.07 m^3. This gives the person\na bouyant force in air of about 0.2 lbs.\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>chris h fleming wrote:
>>My
>>question is how much would an average person weigh if it were not for air
>>pressure? Or in general any discussion about the topic.
>
>
> The scale would measure less the force of buoyancy. Which is just the
> weight of a person sized amount of air.
> So take a person as about 1/2 meter x 1/2 meter x 2 meters = 1/2
> meter^3 volume.
> And the density of air being 1.29 kilograms/meter^3.
> A person sized amount of air would have a mass of about .6 kilograms

That's a very large person. Most people have a density just about
equal to water (i.e. if I have my lungs full of air I float but when I
exhale I sink). .5 cubic meters at that density has a mass of
500 kg or weight of about 1100 lbs.

A more reasonable volume would be based on a weight of about 160 lbs
which corresponds to a volume of .07 m^3. This gives the person
a bouyant force in air of about .2 lbs.

robert j. kolker

Nov17-04, 10:52 AM

<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>chris h fleming wrote:\n\n>\n> I believe the balloon certainly does have weight. Try weighing it in a\n> vacuum. The balloon is just less dense than air, so it floats in air.\n> On the moon it would drop.\n\nA ballon and a rock would fall identically on the Moon. One of the\nastronauts did this trick with a feath and a hammer. Both were let go at\nthe same time from the same height. Both landed at the same time.\nGalileo was right.\n\nBob Kolker\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form">  View this Usenet post in original ASCII form </a></div><P></jabberwocky>chris h fleming wrote:

>
> I believe the balloon certainly does have weight. Try weighing it in a
> vacuum. The balloon is just less dense than air, so it floats in air.
> On the moon it would drop.

A ballon and a rock would fall identically on the Moon. One of the
astronauts did this trick with a feath and a hammer. Both were let go at
the same time from the same height. Both landed at the same time.
Galileo was right.

Bob Kolker