Physics student students have long recognized the inherent coolness of ping pong cannons, but have often expressed disappointment in their lack of speed. Due to the laws of gas flow, a run-of-the-mill ping-pong cannon can only accelerate a ball to speeds of 160 – 480 kilometers per hour – far too fast for any human ping-pong opponent, but still far, far too slow.
Purdue University’s Mark French, and his students Craig Zehrung and Jim Stratton, have fixed that problem. By adding a convergent/divergent nozzle to the cannon, they found a way to make an already cool toy even cooler, and accelerate a ping-pong ball to supersonic speeds.
The key to Professor French’s design is the addition of a de Laval nozzle – a simple tube, pinched in the middle. Air traveling through the tube reaches the speed of sound when it hits the pinch, then accelerates once it passes through and is given more room to expand. This blast of air rockets down the rest of the tube, carrying the ping-pong ball with it. The results speak for themselves:
Learn More About the Canon’s Physics and See it in Action Below:
Images and Video Courtesy of Mark French
