Wednesday, July 3, 2019

"Bouncy" sulfur hexafluoride gas in tennis balls?

Testing myths about gas inside tennis balls.
Note:  I should have added that all of the gases tested would have the same bounce height in a perfect no-loss system.  The reason that SF6 bounces higher is because it heats less during compression, lowering the amount of possible thermal loss.  Argon heats more during compression, and can lose more energy because of thermal transfer from the gas into the cylinder walls, where it is not restored upon decompression.  Things are more complex in a tennis ball, though:  Most of the losses are in the rubber shell, and not in the thermal dissipation of the fill gas.  It's hard to estimate, but I'd say that the highest fill pressure, with a high-gamma gas would prove to be the most bouncy since it would cause the rubber shell to deform the least.  The amount of compression in a tennis ball is very low, and any effect due to the gamma of the gas will be extremely small.  Fill pressure will have a dramatically bigger effect.

Google drive link :
 Nike Air:

EPA SF6 use:

100 kg load cell:
Instrumentation amplifier:

SF6 on eBay:

Tennis ball patent:

SF6 data sheet:

SF6 worldwide usage:

General adiabatic resources:

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