Bernoulli's Hair-dryer

Inspiration
Floating balls over a wind sources are a staple of hands on science museums and kids science books.

Materials
Ping pong ball
Electric hair-dryer with cool air setting (don't want to melt the ball)
Toilet paper tube or paper towel tube

Notes
The setup couldn't be easier for this one as all you do is point he hair-dryer up and set it on high speed with cool air and have the kids drop the ball in to the flow and enjoy.  It helps to illustrate the power of the Bernoulli principal effect here if you not only show how it can make the ball hover with the dryer pointed up but also at an angle so that the ball is clearly hovering to the side of the blower so it's obvious that it's not just wind "pushing up".  After they've had a change to play with how the laminar air flow traps the ball in various ways add the tube from above the ball and watch the ball shoot out of the top at a decent clip.

Stamspud Launcher Lite

June 20, 2012 

Inspiration

I read about this variant potato launcher in the book Totally Irresponsible Science from which I'll be mining many other fun demonstrations and 'experiments".  Also http://www.education.com/activity/article/potato-cannon/ has good info for this design cannon as well.

Materials
4' length of 1" schedule 40 PVC pipe
Disposable mop (handle must fit inside PVC pipe.)
Potatoes for ammunition


Notes
This launcher involves putting potato core section on each end of the pipe and then using the mop handle to ram the bottom core up towards the top core as quickly as possible to compress the air between them and send the top spud sailing.  The results were not as spectacular as those from the combustion powered cousin that we did last year but it was certainly faster and easy to set up.  


Some setup tips for better performance we found that slightly sharpening the ends of the pipe with a knife of file allows for easier cores to be loaded and helps make for nice tight seals (sharpening the outer edge of the pipe makes for ease core cutting but doesn't improve the fit/seal like shaving the inside does).  Any dowel that fits in the tube can be used as a rammer but the disposable mop lets you anchor the bottom by standing on the mop head while you thrust the pipe downward over the handle to create the compression. When you push the dowel up in to a stationary pipe you would need to take precautions not to pinch your hand, while the mop setup avoids that hazard neatly while letting you ram with as much force as you like.


Our results varied a good deal ranging from 25' high launches up to near 70' or 80' I'd guess.  Depending on potato size and pipe diameter you can get many shots per potato, simply reloading the empty end after firing and firing again.  Unfortunately we didn't get any pictures of this event while we did it up at my parent's house in Jackson NH