Pressure of a Latex Balloon as it is Inflated
Why Physics Stack Exchange recommends it
Physics Stack Exchange answerers cite it as experimental evidence of how a rubber balloon's pressure changes with inflation, including the early peak, the plateau and the rise before bursting.
Recommended by 0 people across 0 different months, 2012 to 2021.
What it is
A short 2008 clip from the channel jspchmst that records the internal pressure of a latex balloon continuously as it is inflated until it pops. It shows the pressure curve rather than offering narration or theory.
What people said
Cites John Rennie · 2012-10 · Physics Stack Exchange · on “Relationship between balloon size and pressure”
You're quite correct that in a rubber balloon the tension in the rubber increases as it stretches. The pressure is only lower at larger radii when the tension is constant. Soap bubbles are an excellent example of this because the surface tension depends only on surfactant concentration and not on the bubble size. The pressure in a rubber balloon increases gradually as it is inflated then usually rises more rapidly just before the burst as you reach the elastic limit of the rubber. See [this video] for experimental measurements of the pressure, or I'm sure some Googling would find many more examples. In case the link dies in the future, here's the final graph from the video I mentioned above:
Cites Floris · 2014-07 · Physics Stack Exchange · on “Is this kids experiment a legitimate way to show that air has mass?”
I can think of at least four things going on in this experiment that need pointing out: When you inflate a balloon by mouth, the air is warm: this makes the air inside the inflated balloon slightly lighter than the air it displaced The air inside the balloon has 100% relative humidity at 37C, and condensation will quickly form on the inside of the balloon as the air inside cools down. The air inside the balloon contains carbon dioxide, which has higher density than room air (molecular mass of 12+16+16 = 44 amu, vs oxygen at 32 amu and nitrogen at 28 amu - ignoring small isotopic effects, and ignoring Argon). The pressure inside the balloon is larger than outside - this increases the density
Cites akhmeteli · 2018-12 · Physics Stack Exchange · on “Surviving a fall into a balloon-filled pit”
In order to answer your question, let us compare an air balloon and a volume of air in the atmosphere having the same shape as the balloon. According to [this video] , the pressure does not differ more than by 10% in these cases (at a higher excess pressure the typical balloon pops). Next, the mass of the balloon envelope is less then the mass of the air it contains (as the same balloon floats if filled with helium). Therefore, the average density in the pit filled with balloons should not exceed the density of atmospheric air more than by a factor of 2. Then, using the drag equation [LINK] for a rough estimate, we assess that the drag in the pit should not exceed the drag in the atmosphere more
Cites Dr Colvile · 2021-02 · Physics Stack Exchange · on “Inflating a balloon (expansion resistance)”
The generic plot above has some experimental verification at [this video] . [LINK] A pity they didn't measure radius of balloon, but if we assume constant rate of expansion, the shape of the graph plotted against time should be similar. Indeed, it clearly shows the initial maximum pressure, which is shown above to be caused by the small radius of curvature of the balloon surface, followed by a decrease to roughly constant as the radius of curvature increases. Departure from the assumption of constant modulus of elasticity then causes the pressure to start to increase again.