After the experiment, it seemed like they had managed to break the barrier-but the students felt their results were inconclusive. They rigged up a high-speed photography kit that would allow them to measure the distance the tip of the towel was traveling at the moment they thought the barrier would be broken. In 1993, a group of students at North Carolina School of Science and Mathematics set out to prove that a properly whipped towel could break the sound barrier. Like a bullwhip, it goes very fast indeed. The reason it's so dangerous has partly to do with the speed the end of the towel is traveling. Snapping a towel in the changing room is dangerous-you could, in all seriousness, take someone's eye out. And when it reaches the speed of sound, it creates a sonic boom. It turns out that the cracking noise is actually created by a loop traveling along the whip, picking up speed.
Breaking the sound barrier crack#
They were puzzled as to why, if the crack is a sonic boom, it doesn't occur until the whip's tip is traveling at almost twice the speed of sound. Or at least, that had been the presumption until researchers at the University of Arizona spoiled it for everyone. You know that crack a bullwhip makes when it's wielded in anger by an expert? That's a sonic boom, the shockwave created when the tip of the whip breaks the sound barrier. Remarkably, given their light weight and poor aerodynamics, the ping pong balls delivered as much energy to their target as a brick falling several stories. The cannon used a vacuum pump to suck the air from a sealed tube, the air rushed to a nozzle shaped like an hour glass, and the nozzle propelled the ping pong balls at supersonic speed-about 919 mph. “You can get really, really high accelerations, the ball comes out of the barrel intact and doesn’t break until it actually hits something,” mechanical engineer Mark French Inside Science. But even that pales in comparison to the air-powered cannon built in 2013 by students at Indiana's Purdue University, which fired ping pong balls at more than 900 mph. Anyone who's watched the top table tennis players in action knows they hit the ball hard and that it travels almost too quickly for the eye to see.
0 kommentar(er)
