How does a helium balloon float?
[ 2006-03-01 08:25 ]
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Helium balloon |
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How does a helium
balloon float? |
 Helium is lighter than air and just as the heaviest
things will tend to fall to the bottom, the lightest things will
rise to the top.
Helium weighs 0.1785 grams per liter. Nitrogen,
which makes up 80% of the air we breathe, weighs 1.2506 grams per
liter.
Basically, if you were to fill a soda bottle with helium and
another with air, the one filled with helium would weigh a gram less
than the bottle with air. It doesn't sound like a lot, but that's
usually why balloons are usually really big, the one-gram difference
really adds up in large volumes. Helium balloons follow the same
principle as you do when you float in the water; the law of buoyancy. If the water you displace weighs
more than you do, you will float.
Helium isn't the lightest element, hydrogen, weighing a mere
0.08988 grams per liter, is.
Wondering why we don't use that instead of helium?
Well, hydrogen balloons used to be really popular, but it is
extremely flammable. The slightest spark will set off a huge
explosion.
Did you know?
Helium is a colorless, odorless, tasteless inert gas at room temperature and makes up
about 0.0005% of the air we breathe.
Helium's principal
source is natural gas wells where it is extracted from the crude
natural gas stream and purified and that it can be stored and
shipped either as a gas or a cryogenic
liquid. |
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note:
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liter: 升
Nitrogen: 氮
buoyancy: 浮力
inert gas: 惰性氣體
cryogenic liquid: 低溫液體
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