Mark French, a mechanical engineering technology professor, drew on his experience as an aeronautical engineer to create a device that blasts the lightweight, 2.3-gram balls through plywood or aluminum, or deeply dent steel. Online video shows the air-powered bazooka destroying pingpong paddles, VHS tapes, and a row of soda cans.
The secret? A pressure chamber connected to the vacuum tube via a convergent-divergent nozzle. “That hourglass-shaped nozzle is similar to what is used in fighter jets,” French said. “When the pressurized air rushes through the bottleneck, it accelerates to supersonic speed as it helps propel the ball through the clear PVC barrel.”
He says the supersonic speeds are surprising because the balls weigh so little, have such poor aerodynamics, and sport a high drag coefficient. The energy delivered is equivalent to a 125 mph fastball or a brick falling several stories.
Enough about the physics, click here to see the bazooka shoot supersonic pingpong balls through stuff.