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A spherical balloon 20cm in radius is displacing 41g of air. Even ignoring compression (which I don’t know enough to quantify the effects of, except that it wil
by chrismorgan 7mo ago
A spherical balloon 20cm in radius is displacing 41g of air. Even ignoring compression (which I don’t know enough to quantify the effects of, except that it will make the numbers more unfavourable), nitrogen’s 3.3%-lighter gives you a budget of only 1.35g for the balloon. I believe balloons hare heavier than this, so the balloon will still sink (a little more slowly than an air-filled one, but I’m not sure how noticeable the difference will be).
- nerdsniper 7mo ago> which I don’t know enough to quantify the effects of You probably do, actually! People constantly underestimate the grand utility of their basic education. At near-atmospheric pressure and typical ambient temperatures, the ideal gas equation (PV=nRT) from introductory physics works very well and indicates that a 3% overpressure would make gases 3% more dense (linear direct proportionality). At some threshold of high pressures/ low temperatures, you'd want to switch your equation of state (EOS) from ideal gas law to something else. Peng-Robinson would be a good choice for a non-polar gas like Nitrogen, if its >10-50 atm pressure and/or < -50C temperature. At 20 degC, 1.00atm to 3kPa gauge pressure, ideal gas law predicts nitrogen would increase in density by 2.9608%. Whereas Peng-Robinson predicts it would increase in density by ever-so-slightly more, 2.9623%. This is truly negligible, so better to use the simples EOS for explainability (which would be the ideal gas law).
- chrismorgan 7mo agoYeah, I didn’t know enough to quantify those effects! :-)