Vacuum Cannon (2B30.70)

Description:

A long PVC pipe contains a ping pong ball at one end. Both ends are sealed and the tube is then evacuated by a vacuum pump. When the seal is broken at the end with the ping pong ball, atmospheric pressure accelerates the ball and gives it enough kinetic energy to destroy empty aluminum cans.

Procedure or Operation Notes:

Some practice breaking the rear seal is required to get a big column of air behind the ping pong ball.

The ping pong balls do not fit tightly inside the pvc pipe so some air does leak around as it moves down the pipe. On high speed video, it looks like this air is compressed by the ping pong ball and blows out the seal before the ball reaches the seal.

Average muzzle velocities are around 200 m/s.

References, Comments, or Footnotes:

1) Vacuum Cannon Calculations (PDF).

2) Derek J. Thuecks and Harrison A. Demas, "Modeling the effect of air-intake aperture size in the ping-pong ball cannon." American Journal of Physics 87:2. 136-140.

3) See problem 1.22 in "An Introduction to Thermal Physics" by Daniel Schroeder. This is the current textbook for Physics 224.