Disclaimer:

Reprinted by permission of Dick Berg, University of Maryland, for use on this website.

The demonstrations contained and referenced herein are listed for the purposes of cataloging and describing physics demonstrations which should be conducted only under the direction of a trained instructional support professional or physicist. These demonstrations are not presented for the purpose of being conducted by persons unconnected to this Facility and/or persons not consulting with or being supervised by the recognized instructional support professional or physicist and his/her staff. The University is responsible only for those demonstrations carried out using its own equipment using established safety and scheduling policies, and bears no responsibility for those choosing to use this source material for their own purposes. All demonstrations described and contained herein are public domain, and can also be found in reference materials in libraries, bookstores, and electronic sources.

Further information regarding legal liability in use of demonstrations and labs will be found on the web site Injuries in School/College Laboratories in USA.

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Place the vacuum cannon on the table and clamp the pop can holder directly in front of the cannon muzzle.  Place a 40mm Ping-Pong ball into the muzzle and roll it all the way down to the stop provided by the vacuum inlet.  Place 3-M packing tape onto each end of the cannon taking care to insure that the tape is flat so that it doesn't have any air leaks.  Fold an appreciable amount of tape over the ends of the cannon.  This will ensure that premature failure of the vacuum seal does not take place when pumping down the cannon.  Pump the air out of the cannon with the vacuum pump.  This process may be monitored using the attached vacuum gauge on the cannon.  When the desired vacuum is reached, shut the valve on the cannon and turn off the vacuum pump.  Using a sharp object, puncture the tape at the rear end of the cannon ( the end closest to the vacuum connection, gauge, and valve ).  Warning:  When the tape is punctured a very large noise is produced.  The Ping-Pong ball will be driven out the other end of the cannon by the inrushing air and will puncture several soda cans.    These can then be taken out of the holder and passed around to the class.  Warning:  The Ping-Pong ball can theoretically achieve muzzle velocities of 287 m/s.