Science · 6 pages · 12 min

Why a helium balloon rises and a breath balloon does not

Helium plus the skin weighs less than the air displaced, and a lungful of air does not.

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From the opening

A helium balloon rises because the helium plus the rubber weighs less than the air displaced by the outside volume. The buoyant force then exceeds the weight, and the leftover force is upward. The opening covers total weight versus displaced air, why a breath balloon falls, and what a heavy skin does to lift.

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Inside

Total weight versus displaced air
Why a breath balloon falls
What a heavy skin does to lift
How hot air gets a similar result
Where the idea stops applying
A distinction worth keeping

Sources

Buoyancy of a lighter-than-air envelope
The low molar mass of helium compared with air

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Why a helium balloon rises and a breath balloon does not

From the opening

Inside

Sources

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