Date: Wed, 06 Feb 2002 17:00:20 -0600


Subject: Re:Demos which make students gasp!


This is my new baby. A cannon which uses "nothing" as the propellent. More
accurately stated, it uses the absence of something. Basically I take a 5 foot
long section of 1 1/2 inch pvc and evacuate the air inside the tube. Both ends
are sealed, and when I puncture one end, nature's abhorance of a vacuum takes
over and the projectile is launched out of the other end at a high rate of speed
(estimates place it at 50-80 mph, though as you'll see if you visit the website,
we're not using a very aerodynamic projectile). The film can holds up better
than our ping pong ball, but we're still searching for that perfect projectile.
It works best when launched horizontally, but we have taken it outside and
nearly cleared the roof level of our three story building. I first saw this as
an undergrad at the University of Northern Iowa, but couldn't remember exactly
how it was set up so this is my best estimate. Visit the website and check it
out, let me know if you have any thoughts on it....

Matt Harding
Iowa City West HS