Bernoulli with a twist - levitating ball.

This model demonstrates Bernoulli's principle and the Coanda effect.  In very simple terms these relate to how pressure is lower in a fast moving stream of air, and also how a stream of air tends to follow an adjacent flat or curved surface.  There are many people much better qualified than me when it comes to explaining this, so I recommend wikipedia or similar if you want to know more.

The basic idea is that you place the 3D printed ball (or a regular 40mm table tennis ball) on the end of the pipe, and blow.  The ball will levitate a few inches above the pipe.

Aside from the interesting scientific aspect, learning to control the ball height and keep it steady may be considered helpful for players of certain wind instruments.  Also aiming to keep the ball in the air for as long as possible is likely to improve lung capacity.

There are a number of similar models available elsewhere, but this one has a couple of twists.

First, I include a 3D printed ball, whereas most others generally require a table tennis or ping-pong ball, or some other very lightweight ball.  While it's true a ping-pong ball works a little better, the 3D printed one is sufficient to demonstrate the principle.

Secondly, I include two pipes; they are very similar, with the same sized hole, but only one works!  The difference is in the clearance between the ball and the top of the air hole.  On the one that doesn't work, the gap is very small, and so when you blow the air comes out very fast and so generates a lower pressure, resulting in the ball being sucked down on to the pipe, rather than blown off.

I figure this can be used to prank your friends; let them see the pipes look the same, them give them the prank one and watch them go red in the face trying to copy you on the other pipe.  If you then swap pipes, you can make the prank one work by subtly giving the ball a small lift with one finger; once the gap is bigger the ball will levitate as it does on the other pipe.

Enjoy, and come back to rate the model if you want to encourage me!