A soap bubble on the end of a cylindrical tube is seen to deflate as the higher pressure air inside the bubble escapes through a tube. We perform an experiment to measure the radius of the slowly deflating bubble and observe that the radius decreases to a minimum before quickly increasing. This behavior reflects the fact that the bubble ends up as a flat surface over the end of the tube. A theoretical analysis reproduces this behavior and compares favorably with the experimental data.
REFERENCES
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For those interested in seeing some fantastic soap bubble creations, two great websites are ⟨www.tomnoddy.com⟩ and ⟨www.soapbubble.dk.en⟩.
3.
An excellent introduction to the scientific aspects of soap bubbles can be found in
Cyril
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A complicated recipe (from a physicist’s perspective) for very long-lived soap bubbles is given by
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Although it would seem that the precise detergent is unimportant, we found Dawn Ultra to perform significantly better than other detergents.
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We use a paper towel soaked in soap solution and rub it across the top of the tube to prep the system for bubble blowing.
12.
National Instruments equipment and software can be found at ⟨www.ni.com⟩.
13.
See, for example,
T. E.
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A simple-to-use online gas viscosity calculator can be found at ⟨www.lmnoeng.com/Flow/GasViscosity.htm⟩.
16.
As expected, the fourth-power dependence on causes a full sphere with to take times longer to deflate than a full sphere with (which collapses at ).
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American Association of Physics Teachers
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