Science Experiments

Flying Protractors - the power of ground effect

Sun, 20th Sep 2009

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What you Need


A protractor (with no holes or lumps)

A very flat table

A very smooth table

What to do

Take a normal school protractor. (You need one of the cheap ones, without the holes in the middle, or a protruding lens).

Find a nice flat, ideally plastic-topped table. Modern school tables and lab benches are ideal (most wooden tables are too rough).

Hold the protractor upside down, with the flat side forwards, between your finger and thumb. Slide it a few mm above the desk, with the back slightly lower than the front, and gently let go.

Try it in other orientations. Does it have the same effect?

What may happen

There is a bit of a knack to it, but you should be able to make the protractor glide gently across the table. In my youth we used to get the protractors to glide slowly across 7-8m of a  very smooth lab bench.

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