Saturday, February 16, 2013

Boys and their (supersonic ping-pong ball) toys


I'm hugely amused by the efforts of a Purdue University professor to use fun and games as a method of teaching physics.  Would you believe he's come up with what Popular Mechanics calls a '900-MPH Supersonic Ping-Pong Bazooka'?

For years, Mark French has been using the regular subsonic version of the gun to teach kids about physics.

. . .

On a hunch, French and his students modified the gun with a convergent–divergent nozzle, the type used in rocket engines and supersonic wind tunnels to accelerate air flow. The revamped gun shoots pressurized air through the hourglass-shaped nozzle. As the air travels through the nozzle's choke point, compression accelerates the air. It blasts the ping-pong ball outward at 900 mph (the speed of sound is roughly 765 mph).

. . .

Once the engineers got the bazooka up and running, they tested it on all sorts of materials, including VHS tapes, 3/4-inch plywood, stereo speakers, and even a sheet of steel. "The ball didn't go through the steel, but it put a whopper of a dent in it," French says. "Normally what happens is the ball comes out in pieces—it's shattered but not deformed. For this one, it melted and buckled. I didn't expect that."

There's more at the link.  Here's a short video clip of the beast being test-fired.





A longer video presentation, giving more details, may be found here.

Kudos to Prof. Mark French for a very original teaching tool!





Peter

2 comments:

ahovelDriver said...

Shoots at 900 mph? Shouldn't be too long before the 'assinine' BATF (Bureau of Assholes Taking Firearms) shows up to haul him, and all his students-and-research assistants away.

Wraith said...

SD's right. This'll be illegal about 20 minutes after DiFi and Obummer hear about it.