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how many square feet of helium do you need to lift 1pound?

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None. You need cubic feet.

Helium has a "lifting force" of about 1g per litre, so to lift a pound weight you'd need a balloon about the size of an armchair.

i meant cubic sorry

None. You need cubic feet.

If his pound was infinitely thin he might be able to use square feet ;-)

Cheers,

Pat. Pending

i meant cubic feet. sorry.

Hmm, but wouldn't that make his "helium" infinitely thin ?

Hmmmm....

There we go LOL

We only need one more for a Barber Shop Quartet LOL

You could ... do the math/chemistry. Helium has a molecular weight of 4. 22.4 l weighs 4g. Air is mostly nitrogen, which has the atom weight of 28. So 22.4l weighs 28g, and the difference (24g) is the life of a mole (22.4l, 4g) of helium (nice and close to the 1g/l number Kiteman posted, too.) A pound is about 450g, so, looks like you need a cube 76cm on a side...