[neilep (OP)]

Hello, My name is Neil,

I love balloons, sometimes I like to grab a bag and just blow a few up cos balloons are fun !!...anyway, as me and the kids were playing, a couple of them burst and it got me thinking, how fast does the average household balloon burst ? How fast does the ' skin ' move ?

I'm talking about your average sized balloon, say, 8- 10 inches in diameter so we don't need to get caught up with semantics eh ?

Make my lungs feel they blew them up for a reason please.

Thank you

Neil


'Men are the same as women...just inside out !'

[Ultima]

It depends on the maximum tensile strength of the rubber which I don't know so I couldn't tell you []. At an average guess I would say "fast".

wOw the world spins?

[neilep (OP)]

quote:Originally posted by Ultima

It depends on the maximum tensile strength of the rubber which I don't know so I couldn't tell you []. At an average guess I would say "fast".

wOw the world spins?

Thanks Matt !!....

Well, I'm convinced !!!....fast is what I thought and quite accurate too...cheers []

'Men are the same as women...just inside out !'

[gsmollin]

Why to Latex balloons go BANG! when they burst?

Contrary to popular belief, the loud noise you hear when Latex balloons burst is not due to the sudden release of high pressure gas contained inside the balloon...such pressure isn't all that great. Rather, the BANG is caused by the tightly stretched ends of the torn Latex balloon pieces exceeding the speed of sound (and, thus, creating a "sonic boom" ) as they quickly snap back to their pre-inflated size. Specifically, when a tiny crack develops in the surface of an inflated Latex balloon (such as when a pin pricks it) the resulting rapid release of energy stored in the stretched Latex accelerates the crack to near the speed of sound in rubber.  Since this speed is much higher than the speed of sound in air, the running crack actually breaks the sound barrier!   The loudness of the bang is usually dependent on how much the Latex is stretched before it bursts. This is why even small Latex balloons stretched to their limits will often make a much louder BANG when they burst than a larger balloon that is not stretched as tightly.

http://www.kcbassociates.com/balcan/facts.htm#Why%20to%20Latex%20balloons%20go%20BANG!%20when%20they%20burst?

[neilep (OP)]

Oh My !!!...with my inherent joy and playful banter that is my love for balloons, my Eden of balloondom has been revealed in all it's balloonding glory via the link above...thanks gsmollin....


That's incredible about the sound barrier !!....sometimes I have held a piece of cellophane over my gob (mouth) and sucked in to make a  really loud pop...is the same thing happenning here ?

'Men are the same as women...just inside out !'

[Ultima]

The bestestest thing to do with balloons is to blow them up and draw some crazy picture on it, and then deflate it... You get a mini detailed picture you can cut out and give to your adoring friends as tokens of your awesomeness [8D]. Another great shrinking trick is to get a finished crisp (chip aka in USA) packet and chuck it in the oven, watch it shrink before your eyes; using a hole punch in the corner you can even make them into “groovy” key rings.[] Someone else can fill in the physics on this.

wOw the world spins?

[neilep (OP)]

Yes yes yes !!...I remember doing the crisp packet thingy as a kid...we used to hold them over a heater and watch with pleasure and joy as they shrunk.....and what a great idea to turn them into key rings..YAYYYY !!

'Men are the same as women...just inside out !'

[chris]

The balloon banging answer from gsmollin above is fantastic, and would have made a great QOTW - you should have saved it !

It's rather like why does a whip go crack isn;t it ?

Chris

"I never forget a face, but in your case I'll make an exception"
 - Groucho Marx

[DrPhil]

The above explanation confuses me. First it says that the "stretched ends of the torn Latex balloon pieces exceeding the speed of sound" but later it says that "the running crack actually breaks the sound barrier", i.e. the crack propagates faster than the speed of sound in Latex and that is what causes the bang. The original question was "How fast does the 'skin' move ?" Seems to me that the speed at which the crack grows has little, if anything, to do with the speed that the Latex achieves as it returns to it's original, pre-inflated shape.

Does the tip of a stretched elastic band move faster if I cut it quickly rather than slowly? It doesn't start moving until after the cut is made.

[gsmollin]

I see the source of your confusion. A crack could propagate without causing a shock wave, since it involves no significant movement of the balloon. However, most of the photos of this phenomenon are showing the crack opening up about half the length of the crack. That may still be supersonic, but it doesn't exactly nail it down.

Here's another pic of a balloon bursting, this time it's a water balloon. The web page is mostly about the wrong conclusion being drawn from the experiment. In there, is the info that the water held its shape for 13 microseconds after the balloon burst. I infer that the bursting had to be shorter than 13 microseconds. However, here's another counter-point: A water balloon does not burst with the large pop we hear from a balloon blown up with air. The photo implies that the bursting action is still supersonic, so where is the shock wave? I suspect that the sound produced has very much to do with the energy from the compressed air in the balloon, regardless of what the authors claimed in the first website. The water balloon does not store the energy, because the water is not compressible. It may be another case of drawing the wrong conclusion from the experiment.

http://www.textbookleague.org/103tram.htm

[DrPhil]

Thanks much. It's just that is such an important question. I need to know the answer, so everything else in my life can fit into place. I can’t sleep until I know what’s up. Am I crazy?[]

[tweener]

I'm thinking that the water balloon doesn't break the sound barrier because the water retards the motion of the latex as it shrinks.  With air on both sides of the latex, there would be far less resistance to its motion.

Just a thought - I haven't perused the websites to form an expert opinion.

----
John - The Eternal Pessimist.

[gsmollin]

The 13 microsecond number quoted in the text indicates the balloon burst would be hypersonic. A multi-shockwave should be generated! Actually, I don't believe that number. I think they meant something else. It's probably a mis-print, although this has been reprinted in many editions. It may belong in "bad science" website.

Another website I was on had an .avi video of a water balloon burst, shot at 2000 fps, so there is no more than 500 microseconds between frames. This video shows a balloon going from no burst in one frame to a six-inch (my estimate) rip in the next frame. That gives a max of 500 us for the rip to propagate. That speed would be supersonic. Yet we don't hear a large pop, just a small cracking sound. The small crack may be the shock wave. The large pop of an air-balloon may be the compressed air suddenly released. That's my postulate at this point.

What was so surprising is that there is so much information on balloon bursting on the WWW, but very little actual science posted. Anyway, this was one of those fun questions Neil is so good at asking. I think he should be making up questions for a game show. What do you thik, Neil, a new career, perhaps?

[neilep (OP)]

"Fingers on buzzers, here's your starter for ten"[]....that's a good idea Gsmollin.....I suppose there could be people who make a living out of setting questions....but they probably know the answers too!![]

'Men are the same as women...just inside out !'