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Is a pressurized air object heavier?

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.

Reply to
Edwin Pawlowski
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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

Reply to
Jeff Wisnia

Air has weight--Gas law: PV=WRT or W=(PV)/RT Where W= pounds of air, P=pressure, V=volume, R=gas constant, T= temperature. All things being equal, the higher the pressure the more pounds of air is in the tank. MLD

Reply to
MLD

the idiot?) :)

temperature

compress it

weight is added

Do you mean the 32 pounds of air doesn't weigh 32 pounds? :-) Bob

Reply to
Bob

helium than empty?

balloon which was

point lift the helium

balloon......

LOL!!

Bob

Reply to
Bob

helium balloon on

move when the

Why not?

Bob

Reply to
Bob

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.

Reply to
Larry Bud

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.

Reply to
mm

Depends on whether the container is airtight or not, and, if airtight, if there's enough air in it to keep the birds alive.

Inertia causes air to move forward, increasing the air pressure in the front of the bus -- thus pushing the balloon backward.

Reply to
Doug Miller

According to Larry Bud :

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.
Reply to
Chris Lewis

wrote

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

Reply to
SteveB

Not *any* gas. There is no liquid phase of helium at room temperature at any pressure.

Sure, 32psi is about 2ATM, so it will weight twice that of air at

0ATM (note: differential pressures). Air is mostly N2 and O2, so it has a weight of, say 30g/mole (O2 is 32g/mole, N2 is 28g/mole). At STP there are 22.4moles/l so that's about 375g/l. So, at 2ATM a tire will weight about 750grams per liter of tire volume more than it will deflated. That doesn't sound like it's going to to take a tremendously accurate scale to measure. ;-)
Reply to
krw

Inertia causes air to move forward, increasing the air pressure in the front of the bus -- thus pushing the balloon backward.

WRONG.

The balloon moves forward.

I would explain why, but since we all know that Doug is never wrong, there really isn't any point; because Doug will never concede he is wrong.

So, I'll leave it to others to convince him.

Reply to
Matt

....or does it cost £32. ;-)

Reply to
krw

Actually it is 22.4L/mole at STP; atmospheric pressure would be quite great your way ;) So 1 L of air at 2 atm would weigh about 2.7g.

Reply to
BAttwood

Damn, sitting thinking about it after, I *knew* I screwed something up. My calculation would have made a 1cu.ft. bucket of 2ATM air weigh upwards of 50 lbs! Oops. Thanks for the catch!

Reply to
krw

"I would explain why, but since we all know that Doug is never wrong, there really isn't any point; because Doug will never concede he is wrong. "

DAMN.

Jeff, why'd ya have to go and change the riddle on me?

Oh well.

Sorry Doug.

I have to go scrape egg now.

Reply to
Matt

Well I could have asked which side it moves to when he takes a left turn, (Right of course.)

And, I didn't actually read it as a riddle. I first saw the balloon thing happen many years ago through the back window of a "station wagon" in front of me, and put 2+2 together.

Speaking of math... and limericks...

A dozen. a gross and a score, Plus three times the square root of four, Divided by seven, Plus four times eleven, Equals nine squared plus zero, no more.

Jeff

Reply to
Jeff Wisnia

"And, I didn't actually read it as a riddle. I first saw the balloon thing happen many years ago through the back window of a "station wagon" in front of me, and put 2+2 together. "

Ah.... well, it's an old brain teaser, but it usually reads what happens to a helium balloon when the driver _accelerates_.

Reply to
Matt

That's weird...... I guess thats bcause its not compressed any longer, huh?

Now, as if this thread was not already crazy enough, I got to thinking. If a person fills all the tires on their car with helium instead of air, will the car be lighter on the ground and save fuel? (((Just a thought))). Obviously the car would not float because it's too haevy and there is not enough helium. If this worked at all, it would not be a good idea in winter when weight is needed for traction on snow and ice.

Of course if you filled the whole car with helium (after seriously plugging all the leaks), would the car fly? This would not be a good idea though because the driver would be talking like tweety bird on his cell phone before he died a couple minutes later from lack of oxygen..

This just keeps getting more and more interesting !!!! :)

Mark

Reply to
maradcliff

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