No such thing. The buoyant force increases faster than the gravitational force would when it comes to helium.
I don't know that 100%, but i'd put my money on it.
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Anonymous2009-02-13 22:03
It doesn't work that way. The more helium in the balloon, the less the balloon's rubber density contributes to the overall density and overall buoyancy of the object. The relationship would be hard to gauge because of the effect of pressure differential between inside->outside of balloon, rubber flexibility, etc., but the point is-
Once you surpass that critical point where the balloon contains enough helium to float, there is no point where the balloon will cease to float upon adding more.
Once you put enough in the balloon, it will pop, at which point the balloon, now reduced to shards, will likely be too heavy to float in the air and will fall to the ground.
So, enough to make it pop.
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Anonymous2009-02-17 5:36
>>12 >>13
no, that's retarded. it says BEFORE it is too heavy to float. that implies if there was a bit more helium, it would become too heavy to float, which in turn implies if that excess helium isn't added it is still afloat, albeit just barely.
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Planetary Sci-guy2009-02-21 3:49
it actually depends on the elasticity and size of the balloon. A mylar balloon, for example, isn't really all that elastic. if you engineered one to be strong enough to contain a number of helium atoms heavier than the number of oxygen atoms it displaces, it will sink.
The molecular weight of He is about 4.02g/mol, where as air can be approximated as 28.97g/mol. So if you gradually inflated a balloon of fixed volume (ie would not elastically expand) with helium, you could expect it to sink shortly after exceeding 7 atmospheres of pressure, if the pressure outside were only 1 atmosphere. to put this into perspective a regular elastic balloon completely inflated, has an internal pressure of only about 1.05 atm, 1/140 the required difference, and again an elastic balloon wont keep a fixed volume.
Here's a thought experiment for you; what happens to a balloon in a vacuum chamber? assuming you could keep it from popping or expanding to fill the entire chamber, it should sink. if there are no heavier elements outside the balloon to maintain its buoyancy, its just a bag of atoms, and it sinks.
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Anonymous2009-03-01 17:54
>>1
How much air would you have to put into a ship before it is too heavy to float?