Large Balloon, Small Balloon

Let's take a look!

Watch the video on YouTube.

What kind of experiment is this?

Experimental procedure and explanation:

• Take two balloons of the same material. Inflate one considerably more than the other. The two will have different masses because they hold different amounts of air.
• When the two balloons collide, the smaller one rebounds away faster than the larger one. This is because the smaller balloon holds less air, and hence, has a smaller mass.
• In everyday life, you are not conscious of the mass of air, but actually it is fairly large. The mass of a cube of air, 1 m on a side, is about 1.2 kg at 20°C and one atmosphere of pressure. This is more than that of milk in a one-liter container.
• We do not feel this mass because the air receives a buoyancy force of the same magnitude from the surrounding air, so the air behaves as though it has no weight of its own.

[Keywords]	air mass
[Reference]	“The Wonders of Flow” Japan Society of Mechanical Engineering, Kodansha Blue Backs pp. 26-29