ElI5: Explain boyancy please

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If I have a steel canister of helium and a balloon attached to the valve. If the helium is in the canister, the assembly stays on the ground. If I let the gas into balloon it floats. Why?

There is no change to the amount of energy, the gas is de-pressurised from the canister to the balloon and the density inside the balloon changes, but the overall weight stays the same.q I should know, I just can’t figure out why exactly.
Thanks

In: Physics

6 Answers

Anonymous 0 Comments

The total mass of the balloon + tank + helium is the same both before and after. The volume once the balloon is filled is much larger, so the volume of the system is now larger.

Density is mass / volume. While the mass remains the same the volume increases, making the density smaller. If the density is small enough the tank and balloon will float in air.

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