Northwestern Physics Demos                                 Go back to FLUIDS
DCS# 2B30.70NWU# F-24 Location:    on air track near 4
title: Vacuum Cannon
aka:   atmospheric pressure launching ping pong ball or vacuum bazooka

   A 40 mm ping pong ball is loaded into a 1.5 inch PVC pipe and rolled to one end.  Packing tape is applied to each end of the tube and a vacuum is pulled inside the tube.  When the tape near the ball is ruptured, a slug of air pushes the ball along the tube.  With atmospheric pressure doing the pushing, and no air resistance, the ball leaves with a speed near that of sound!
  The ball can be directed to targets, a cardboard box, or a rack of empty soda pop cans.

    Would this work on the moon? (ie. in a vacuum?)
     What does the speed depend on?
     Would the speed be higher or lower at the top of a mountain?
pix of set upammo