Air Cannon Physics: Approaching the Sound Barrier

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Graham, Hugh
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Scholarship Sewanee 2022 , University of the South , Ping Pong , Cannon , Physics
A ping-pong ball “cannon” was built and tested, first with the usual air, and then with single composition gases, such as helium and argon. A plastic tube (the canon) containing a ping pong ball snugly fitted inside the tube is sealed with tape on both ends and evacuated with a mechanical pump to a pressure of about 100 mTorr. A pin is used to prick the tape nearest the ball causing the outside air to rush in, accelerating the ball forward and out the other end of the tube at speeds approaching the speed of sound. Light switches were used along the length of the tube to measure the acceleration and speed of the ping pong ball. The number and placement of the light switches were adjusted to get the best possible measurements of the movement of the ball. Experiments with different gases with very different speeds of sound were performed to study the balls’ performances