Simulations are combined with laboratory measurements to show the important role of shock waves in a popular physics demonstration, the “ping pong cannon.” The simulation and measurements confirm a developing shock wave that reflects from the end of the closed tube and approaching ball and the eventual formation of a transient localized pressure build-up near the exit tape barrier. This 2atm burst of pressure peaks within a few microseconds of the ball’s arrival, resulting from the combination of near ambient gas density and shock heating to about 1200K. Pulsed schlieren images beyond the exit confirm the sequence of internally reflected shock waves and the intense, hot air pressure pulse that explosively removes the exit tape just prior to the ball arrival.

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See EPAPS Document No. E-AJPIAS-74-020612 for additional color figures and animation. These figures and animations are also at ⟨www.bethel.edu/~kstein/ShockTube/main.html⟩. This document can be reached via a direct link in the online article's HTML reference section or via the EPAPS homepage (www.aip.org/pubservs/epaps.html).
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The shock now moves in opposition to the background velocity of gas driven by the earlier “downstream” passage.

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The Piezotronics Model 113A21 Dynamic Pressure Sensor is designed for detecting high frequency pressure phenomena and is well-suited for shock tube analysis.

Supplementary Material

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