I just came across this toy. It consists of a wooden block (about a
3-4" cube) with a round hole (about 2" in diameter and 2" deep) drilled
into the center of top face. A loosely fitted round dowel is placed in
the hole. The top of the dowel is flush with the top face of the block.
The goal is to remove the dowel without touching the block.
The solution is to blow and the dowel pops right out.
The claim is that this is an example of the Bernoulli effect.
Initially I thought this might make an interesting demo, but after a bit
of thought, I am worried that the Bernoulli effect is not the correct or
at the total explanation.
1.) It would require the air to be traveling at 15-20 meters per second.
2.) It seems to work better if there is a downward component to the
air's velocity so that it can go down the gap between the block and the
dowel.
3.) I did a crude instrumentation by connecting a pressure sensor to
the bottom of the hole. ( Used a Pasco sensor and GLxplore ) When I
blew the dowel would pop out but the pressure beneath the dowel at the
bottom of the hole increased momentarily.