NO!  Not my favourite CD!

NO! Not my favourite CD!

Basically built a small hovering disk to show the properties of air pressure.

Take an old CD, a balloon, and a liquid soap container. Remove the cap from the container and glue it to the hole on the CD.

Blow up the balloon and attach it to the cap.
Put it on a flat surface and watch it hover around.

Barry's Response - A well documented idea. It shall demonstrate that air is a real matter and takes up space, thereby providing the cushion for the hovercraft to float on and glide across.

The concept addressed in this experiment has received the name momentum curtain. It (almost) eliminates friction between two objects by placing a thin layer of air between them.

For the most part, the greater amount of air, the greater separation and lower friction (especially if rough surfaces such as grass are involved). However, like all principles, we run into a diminishing return once extra-bulky machinery is required to keep the air flowing.

As with the design of most technologies, involving air or not, a compromise is the best thing for practical purposes and budgets.

A similar idea, Bernoulli's Principle, states that increasing the sideways speed of that cushioning air causes the air to exert less pressure on the surfaces. This explanation gets used every time an airplane flies, even though there's more to it than that. The air around the top side of each wing travels further and faster over that surface so that its pressure decreases relative to the pressure exerted by the slower air under the wing. This imbalance contributes considerable lift for the plane.

In the case of hovercraft, a faster airflow could counter-intuitively lead to a smaller separation. Something to think about.

Thanks, stranger.

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