# Is a pressurized air object heavier?

Absolutely, WRONG!
The answer is explained better by an understanding of basic physics of density, than doing a google search.
The tank is full of COMPRESSED helium. It's density per unit volume is much higher than the helium in a balloon. The balloon floats because of the differential of densities between AIR & HELIUM.
It is NOT the same scenario in the tyre, since we are dealing with the same gases, in the same reference frame. The tyre contains air at a higher density than the air in the frame of reference (around the tyre). Therefore it has MORE MASS when filled, than empty.

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Define full. Define empty ;-)
A pressurized tank of gas isn't "full" until you fill it so much that it turns to liquid. The pressures required (depending on the gas), of course, often makes that impractical.
Empty? Do you mean that the tank is a vacuum? Or, full of air you have to displace?
If by empty, you mean "vacuum", then of course, once you add _anything_ to the tank, the weight goes up.
If by empty, you mean full of air, and the adding of helium displaces air, the weight will decrease until you displace all of the air, then it'll start rising again.

Depends on the empty weight of the tank and how much helium was involved, but yes, certainly, it could lift the empty tank.
--
Chris Lewis, Una confibula non set est
It\'s not just anyone who gets a Starship Cruiser class named after them.
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Yes, true with any compressed gas

Sure. In the tank it is compressed. In the balloon, it is expanded and displacing heavier air so it will lift.
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The balloon will lift, but the question was could the balloons lift the tank. Obviously depends on how much helium was in the tank, and how much the tank weighs.
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And atmospheric pressure and...
Indeed, you can fill a balloon[+] with the contents of an _empty_ tank[*] and have it lift the empty tank. ;-)
[*] An empty tank contains vacuum. [+] okay, okay, a _rigid_ balloon.
--
Chris Lewis, Una confibula non set est
It\'s not just anyone who gets a Starship Cruiser class named after them.
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Larry Bud wrote:

Actually the primary factor after the weight of the tank and other equipment is the volume of air that the balloon displaces.
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Bill wrote:

Empty is a relative term. A tankful of helium at 1 atm is lighter than a tankful of air at 1 atm.
Of course if you release helium into a large balloon at some point it will lift the tank of compressed helium.
It's all about floating; floating in air is the same principle as floating in water. Basically if an object weighs less than surrounding gas or liquid weighs, it will float. For example as soon as the balloon inflates, it gets larger and displaces more air. As soon as the volume is large enough that the weight of air it displaces slightly exceeds the weight of the balloon, the internal helium gas, and everything attached to it, it will start to float.
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snipped-for-privacy@UNLISTED.com wrote:

Well you are wrong on several counts. 1. Of course the tire is heavier with air in it. The size is the same but you add air, so the air inside becomes more dense, period. 2. It is not a fun topic. Whether people agree or not doesn't matter, it is an obvious fact, as obvious as you weighing more if you put pebbles in your pocket. 3. No you don't need a scale that measures in milligrams, just grams. 4. There is no chance that an auto tire would float in air, regardless of what gas you put in the tire.
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Air is a gas that has weight. That weight is 0.080703 pounds per cubic foot. Even helium has weight, 0.011143 pounds per cubic foot, but being about 1/8 the density of air, a balloon of it floats in air just as one lighter liquid will "float" in a heavier one. (vinegar/oil)
It will take someone with more math smarts than I have to calculate the volume of your tire. You could do it by filling it full of water, and draining it and measuring its cubic measurement. Then, when you condense that by 32 psi, the volume of air in the tire increases quite a bit. Therefore it gains weight with each cubic foot of air you put in there.
Any object will float if it weighs less than the water it displaces. I would think that SOME tires and wheels would float if they are a light rim, and possibly a very heavy tire and rim might sink. You would have to do tests to determine that.
But, definitely, a full tire weighs more than an empty one, even though an empty one does have SOME air in there unless it has been removed by a vacuum pump, and then, it would break the bead.
Steve
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wrote:

I think you have everything in your whole post right but this line. The volume of the air in the tire only increases a tiny bit as the tire fills out its full shape. No more flat spot on the bottom, for example, and the tire probably bulges a bit.
But the amount of air inside increases quite a bit. How much I don't know. The air pressure inside is, iiuc 32 psi *more* than normal airpressure, more than the air pressure outside the tire,, which is usually something like 30 inches of mercury. How much more air it takes to increase the pressure, I don't know. Would twice as much air give twice as much air pressure? For some reason I don't think it is that simple. (Although it would if it were piled on top of our current atmosphere. Why I'm not sure about inside a tire, I don't know.)
Someone should look up Boyle's law, and if that is not what it is called, then it's Xxxxx's universal law of gases. The last 4 words should work too.
That relates volume, temperature, pressure, and a constant together. (and maybe one other thing, but I can't remember what that would be.) But even that doesn't iirc say how much air (in mass, grams, or pounds) generates how much pressure.
What would be fun if I could afford a helium balloon is to put it in the back seat of the car and then drive around right and left corners. Unlike everything else that tends to move to the outside of the curve, the helium balloon will move to the inside.
Because all the air is moving to the outside and the air is heavier than the helium. We're used to this when it comes to balloons going up, but I think it would still seem novel to watch them going sideways.

Remove NOPSAM to email me. Please let me know if you have posted also.
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It doesn't matter if the tyre has air in it, because the system is roughly in equilibrium, since the tyre isn't supporting any pressure, therefore you could weigh it pretty much ignoring the remaining air...

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I guess someone missed physics class.
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Standard air (70 degrees at Sea Level and 0% Relative Humidity) is 13.33 cubic feet per pound. That is at 14.7 Pounds per Square Inch Absolute (PSIA). That is pressure as related to a vacuum. If you pressureize an object with air at 32 PSI Guage, that is (14.7+32) PSIA = 46.7 PSIA. The pressurized air would weigh 3.1769 times as much as Standard Air. Standard Air weighs .075 pounds per cubic foot. The pressurized air weighs .075 * 3.1769 = 0.2382675 pounds per cubic foot. That is a difference of 0.1632675 pounds per cubic foot. So if you had 5 cubic feet of volume in a tire, the difference in weight would be 5 * 0.1632675 = 0.8163375 or almost a pound heavier. Of course if you were using something besides Standard Air as a base, the air would have a different starting weight. For example, colder air would be denser and would weigh more. If your scale could weigh in increments of 1/10 pound, it would show you the difference.
Stretch
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snipped-for-privacy@UNLISTED.com wrote:

The pressurized object is heavier. Ask anybody who works in a scuba shop... full tanks weigh a good 5-6 lbs more than empty ones.
--
Mortimer Schnerd, RN

snipped-for-privacy@carolina.rr.com.REMOVE
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snipped-for-privacy@UNLISTED.com wrote:

There is mass and weight. Adding more air will increase the total mass. In the case of something like a tyre or steel container that will also result in high pressure, it will also make it weigh more. That would apply to any gas. However if you were to replace the contents of a sealed container (like a tyre) currently filled with air with say hydrogen at the same pressure, it will be lighter and have less mass.
In short, you are wrong.
--
Joseph Meehan

Dia duit
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snipped-for-privacy@UNLISTED.com wrote:

Your friend. Even air weighs something. You're putting more air into the tire, and it's pretty much staying the same size (hence the air is compressed). Therefore it would be more dense than when empty.
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"Is a pressurized air object heavier? In other words, is an object heavier when it contains compressed air than when it's empty? For example, if I have a tire and weigh it before pumping it full of air, will it be heavier after it's pumped up? I say NO. A friend of mine insists it will be heavier once it's filled with air. Who is right? "
Sounds to me like we have a long way to go with the "No child left behind" program.
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Nah. It has to do with "outcome based" education introduced by the NEA. It doesn't make any difference that you end up stupid after bad instruction, it is more important that you not feel bad about BEING stupid.
Something I have seen very commonly among our youth.
Ever watch "Street Smarts"?
One of the questions was, "How many people are in a trio"?
Two of the people got it wrong.
Sigh ..................
Steve
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snipped-for-privacy@UNLISTED.com wrote:

I suspect I've been trolled, as it's hard to believe that anyone with enough neurons to be able to post a message to a newsgroup could be naive enough to say NO to that question.
Jeeze, next you'll be asking if a shipping container with 200 canaries in it weighs less if the birds are all flying around inside it than if they're all standing on the floor.
Try something a little more interesting like the kid's helium balloon on a string floating inside a schoolbus. Which way does it move when the bus driver brakes quickly, forwards or backwards, and why?
Jeff
--
Jeffry Wisnia

(W1BSV + Brass Rat \'57 EE)
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news:yZidna7sUJK93v_eRVn-

helium balloon on

move when the

Why not?
Bob
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