https://www.instructables.com/The-Magic-Propeller/
A magic propeller toy is a regularly notched wood dowel with a light wood bar loosely nailed to one end, free to spin. The bar is powered by raking the notches with another wood dowel, and the direction is controlled by either resting a finger on one side or the other of the notches or rotating the notched dowel such that you rake one or the other side of the “mountain”.
Why does this work? You can ELI-PhD if you need, but even with my engineering background I can’t figure out what’s happening.
In: Physics
The “wand” vibrates the notched stick. Depending on which side of the stick you touch to dampen the vibration, it changes how the vibrations oscillate the “propeller”.
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