The physics behind trackball inflation

[Woody1458]

well in theory with the added weight of the skin any air on the inside would be compressed past 1 atm (~14.7 psi) (PROOF: unplugging a partially inflated ball will still deflate signaling that the interior pressure was greater then the exterior.) so any inflation would add mass, but should be negligable till ball reaches maximum volume, dictated by the material's elastic constant.

(I always love myself a good debate )

[Kevin Sevcik]

The pressure cs. diameter function is probably highly non-linear once you reach the size of the nylon and start trying to expand that. All the same we whipped out a ball pump to hook up to the trackball after it was inflated and it read something less than 2 psi. Probably 1. So there will be some additional weight. I imagine the manufacturing variances will compound the weight fluctuations from air pressure with slightly thicker, heavier balls requiring even more air to inflate. Overall, though, I wouldn't expect for than +/- .25 lb variation out to 3 SDs

[MrForbes]

The mass of the air inside the ball could make a difference in a design that "shoots" the ball....that's a significant added load....that I had not thought of!

thanks for the lesson!

[Miniflash]

i just fill it up ,weigh my self, then weigh myself while holding the ball and take the diffrence... easy math for us k.i.s.s people ... then to double chech take a string and take the circumfrence and divide by pi.... easy enough to the point of i have a 10lb 40 in diamater trackball

[mneary]

i just fill it up ,weigh my self, then weigh myself while holding the ball and take the diffrence... easy math

But you have to move the ball, too. For that you'll need to know the mass, as described above.