How much lift does the average helium filled party balloon produce? (not including any extras like ribbon string)
4 Answers
The mass difference of the air it would have contained and the Helium it does = the volume of the balloon multiplied by the difference in density of the helium and air.
Suppose the balloon is spherical and 12" in diameter (physicists can only do the arithmetic for spherical objects, and preferably in a vacuum).
That gives it a volume of $\frac43 \pi r^3$ so annoyingly mixing units, $\frac{4}{3} \pi\, (0.15\:\mathrm{m})^3 = 0.014\:\mathrm{m^3}$
Air has a density of $1.2\: \mathrm{kg / m^3}$ at room temperature and pressure and Helium $0.176\: \mathrm{kg / m^3}$. So your balloon has a lifting capacity of $0.014 \cdot (1.2-0.176) = 0.014\:\mathrm{kg}$
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1$\begingroup$ "(physicist's can only do the arithmatic for spherical objects, and preferably in a vacuum)" This is only true in the sense that you have to do calculus to do it. (Meaning correct that it's not arithmetic) If you wanted to do that you would generate a model with a differential equation, integrate over the curve of the line (Times two, if you're balloon is symmetrical (A reasonable assumption, assuming uniform density of the latex)) and then do what the previous answer said. Do not walk away thinking there is something so simple that cannot be calculated by a physicist! And I'm only an engineer $\endgroup$– user20587Feb 4, 2013 at 9:56
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1$\begingroup$ The helium is under higher pressure than the air, being squeezed by the rubber, but this probably makes a negligible difference. OTOH, I'm not so sure it's OK to neglect the weight of the rubber itself. Is it much less than 14g? I don't know. $\endgroup$ Feb 5, 2013 at 15:38
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$\begingroup$ Don't you have to subtract the mass of the balloon skin itself? $\endgroup$– b_jonasDec 7, 2013 at 10:10
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$\begingroup$ @b_jonas - the question is how much lift. But yes you need to subtract the envelope from the "useful" payload $\endgroup$ Dec 7, 2013 at 20:21
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$\begingroup$ How come density has dimensions of mass times volume? It was correct until edit #4. $\endgroup$– RuslanNov 29, 2016 at 14:46
As an experimental answer, for 12" latex balloons, I could lift about 5 grams (in addition to the balloon). It of course will depend on how full you fill the balloons.
Another experimental answer weighing in around 5 grams: http://www.cockeyed.com/science/helium/helium.shtml
An 11" diameter helium balloon with 26 inches of ribbon lifted itself plus 4.8 grams, a total mass of 8.3 grams. It displaced 8.2 liters of water, so that matches up reasonably with a theoretical lifting capacity for helium of 1 gram per liter.
In the case of hellium the pressure exerted by the rubber is negligible. However, when my mad scientest buddies and I tried using methane, we could only get lift if we used dry cleaning bags which did not compress the gas.