Physics Question July 3, 2016Posted by Sobek in News.
So here’s the Slow Mo Guys, smashing open spraypaint cans in super slow motion because they can (and because they’re really cool).
Obviously that’s just pure awesome. But here’s my question. If you go to 1:40, Dan shoots a red spraypaint can with a pellet gun, and you can see (very clearly, if you pause at the 1:43 mark) that the paint is not coming out uniformly, but rather in a wave pattern. That’s my physics question – what causes the wave-like nature of the spray, rather than a more uniform effect? My first thought, when I watched some of the other explosions, was that the paint is affected by Brownian motion, but that wouldn’t explain wave patterns.
The next thing I thought was this reminded me of an astrophysicist’s explanation for the arms of a spiral galaxy. The arms are kept separate by pressure waves. I assume there are pressure waves involved here, but I can’t think of what the source would be, either in the case of the paint or the galaxy.