A Question For The (Mr.) Wizards On The Forums

[BubbleWright]

This is a question based on an observation I made today...

I bought a large mylar balloon, which was filled with helium in the store until the skin was taut. Upon exiting the store, the 30 degree air hit the balloon and it got soft and crumply. I put it in my van and drove home. The heat in the van plumped it up again. I arrived home, and the dash through the cold between my vehicle and apartment caused the balloon to wrinkle up again. Once inside in the heat, the balloon plumped tight again. My question... warm or cold, does the balloon have the same amount of lift? I suspect the amount of helium is the same even though the volume changes, therefore the lift is the same. Any thoughts? ........ yeah I know, when I think too hard my head hurts!  

[RSLeask]

OK, we'll make two assumptions here.  First, is that the balloon is securely tied, and no air can escape from inside of it.  Second, is that the balloon itself isn't variable in mass.  These are pretty standard assumptions, but they have to be made nonetheless.

The reason why a balloon expands isn't just from the amount of air being pumped into the space.  It is also due to the bombardment of atoms or molecules inside of it (usually atoms, though, as molecules tend to be heavier than air, and when you're buying a floaty balloon, this isn't a good thing).  This is variable pressure, meaning the pressure being applied to the interior of object, compared to the pressure being applied to the exterior.  Now, the way this works is that, at certain temperatures, the atoms in a given space move at a certain speed.  Any change to the temperature, and the atoms inside will speed up or slow down, depending which way the temperature shifts.  At lower temperatures, they being to slow down, decreasing the interior pressure.  Higher, and they speed up, increasing it.  So what you witnessed with your balloon, holding the same amount of helium as it did when you exited the store, was the slowing of the helium atoms inside that balloon, which no longer were bombarding the skin with sufficient force to keep it rigid in its expanded form with the constant pressure from the outside air.  As the air around it grew hotter, the speed of the atoms increased, the force to the skin of balloon increased, and it expanded to accommodate.

(This is also the reason why a balloon over a flame will burst, by the by, even though it never comes into contact with the flame.  The air inside the balloon superheats, and the bombardment of the atoms against the skin of the balloon becomes more than the skin's tensile strength can support.)

To answer your question about lift, however, you have to take into account the total weight in a given volume, occupying a given amount of space of air.  As the balloon shrinks, it maintains the same mass, but occupies less space than it previously did.  Shrink enough, and the lighter-than-air helium will not be sufficient to keep the balloon aloft.

Edited for clarity.

[will paisley]

... or in other words, PV = nRT

[RSLeask]

dangnubbit, Bill Nye never used equations in his explanations!   

[Merlin]

To put it simple.... things shrink when they get cold.




IT'S TRUE !

[Welsh Wench]

You actually made it home with the helium IN the balloon?
If it was my husband and the boys, they would have sucked it dry.

It's like living with Donald Duck and Huey and Dewey. 

[BubbleWright]

...it's a very big balloon (he said in a funny, high pitched voice).

Now why do I need a big silver mylar balloon? Every New Year's Day at 1 PM the city of Middletown, Delaware holds an impromptu, do-it-yourself Hummers Parade which spoofs Phillys Mummers Parade. Participants mock and lampoon events and personalities that were in the spot light the previous year by coming in costume and/or with floats with hand outstretched in front of face with thumb firmly touching one's nose. See: http://www.middletowntranscript.com/entertainment/x664195013/Hummers-Parade-back-New-Years-Day . As for the balloon, I attached a cabin below it and will have my very own BALLOON BOY tethered aircraft. I will make up a large billboard sign with words to the effect "CALL 911, CALL THE FAA, CALL CNN,...CALL OPRAH! SEE MY AGENT FOR EXCLUSIVE INTERVIEW RIGHTS AND REALITY SHOW OFFERS". Sick.. demented... yes but you already knew that. Over the years I've participated in at least a dozen of the parades, sometimes with my bubble machines. 

[Marietta Graziella]

This is brilliant!  I hope you post pictures!

...it's a very big balloon (he said in a funny, high pitched voice).

Now why do I need a big silver mylar balloon? Every New Year's Day at 1 PM the city of Middletown, Delaware holds an impromptu, do-it-yourself Hummers Parade which spoofs Phillys Mummers Parade. Participants mock and lampoon events and personalities that were in the spot light the previous year by coming in costume and/or with floats with hand outstretched in front of face with thumb firmly touching one's nose. See: http://www.middletowntranscript.com/entertainment/x664195013/Hummers-Parade-back-New-Years-Day . As for the balloon, I attached a cabin below it and will have my very own BALLOON BOY tethered aircraft. I will make up a large billboard sign with words to the effect "CALL 911, CALL THE FAA, CALL CNN,...CALL OPRAH! SEE MY AGENT FOR EXCLUSIVE INTERVIEW RIGHTS AND REALITY SHOW OFFERS". Sick.. demented... yes but you already knew that. Over the years I've participated in at least a dozen of the parades, sometimes with my bubble machines. 

[Betty Munro]

How are you going to keep your balloon warm tomorrow afternoon?

[BubbleWright]

The weather report is calling for a torrid 40 degree F plus temperature. As long as the balloon stays buoyant enough to float, it will be ok as it is not really lifting anything except for a small 2" figure of TOPO GIGIO (small mouse puppet seen on Ed Sullivan in the 1960s..."Oh Eddieee... give me a kissss!"). Besides, it will look more realistic as the real balloon partially deflated...

[Betty Munro]

Just a suggestion ... maybe a thin wire "string" will help keep it afloat?

And I second the request for a picture of the finished display.

[Noble Dreg]

You actually made it home with the helium IN the balloon?
If it was my husband and the boys, they would have sucked it dry.

It's like living with Donald Duck and Huey and Dewey. 

Same theory explains why I never make it home with a full bottle of scotch...

[Anna Iram]

...then we'd have Winkin', Blinkin' and Nod.  


That sounds like a hoot BubbleWright. Yes pictures please! Also, I agree with Betty. My brother does a site gag with a box of popcorn and seagulls flying over his head...any way...he keep the seagulls flying by attaching them with wire. That would work perfectly for your balloons I think! 

[BubbleWright]

I still have to make up my signs for tomorrow but here are some links to pictures of Topo Gigio, the pilot  and The Tethered Aircraft . I tried to drop in the photos but couldn't get it to work...

http://www.facebook.com/photo.php?pid=30462963&id=1487678759  after 1st photo click on Next.

Last year I went as a down on his luck Billionaire, soliciting donations from the crowd. See link below for photo:
http://gallery.pictopia.com/delawarenj/photo/7477126/

The sign on the trailer reads...

Billionaire Bail-Out

Please help the GREEDIEST NEEDIEST in their time of despair. We have lost millions of dollars (some of it ours) and have had to sell many of our mansions, estates, high-rise condos, and cottages in the Hamptons and on Nantucket. Helping us will put thousands of illegal aliens back to work as cooks, maids, gardeners and chauffeurs thus taking them off of Welfare.

Anything you can afford to give, be it $100, $500, even $1000 would help. We know Americans are the most generous people on Earth... who better to help the small segment of the U.S population who need help the most- The Rich! Place your donations in the champagne buckets or call the number below to donate:

1- 800 - WHO - CARES

[BubbleWright]

PARADE REPORT- It was a perfect day for a parade (at least this time of year). It was 45 degrees F  and almost sunny. There were many variations on Tiger Woods, a few zombie Michael Jacksons, Balloon Boys (one had a Smart Car as the balloon cabin), an underwear bomber dressed in just padded briefs, one fellow in drag as Susan Boyle complete with music, a down on his luck investor with a sign saying Bernie made off with his money, a float with Captain Sulley amid airplane wreckage, and a crew pushing a Punkin Chunkin catapult (Punkin Chunkin is the Delaware State Sport). There was more but I didn't catch everything. The Parade lasted less than an hour and participants were given trophies... a golfer in full swing. They say there is something in the water here in Delaware...

Unfortunately I had camera problems, so no photos. I will post a link if there is anything in the local papers. Oh yeah... my balloon only slightly wrinkled but remained aloft for the whole parade.

[Betty Munro]

Excellent to hear that the balloon stayed afloat! 
Hoping for pictures.  (fingers crossed)

[BubbleWright]

Well Betty, The Middletown Transcript came through with pictures. My picture is in the 3rd row down, 4th to the right. Yes, we are silly people here in Delaware. See:

http://www.middletowntranscript.com/entertainment/x1671993019/PHOTO-GALLERY-Hummers-Parade-rings-in-2010

[Betty Munro]

Excellent job on the balloon!  How fun!