5 ms·
as the article explains the difference between a pressure wave and shock wave is in their speed of propagation, pressure waves travel below speed of sound, sho
by glofish 6y ago
as the article explains the difference between a pressure wave and shock wave is in their speed of propagation,
pressure waves travel below speed of sound, shock waves travel faster than the speed of sound.
- StavrosK 6y agoHow can a shock wave travel faster than the speed of sound? I thought the maximum speed a disturbance could travel in a material was exactly the speed of sound in that material, since that's what sound is.
- Miraste 6y agoThe shock wave travels faster than the speed of sound in the medium at rest, but not faster than the speed of sound in the moving medium around the wave. Longer and better explanation: https://physics.stackexchange.com/a/193323 https://physics.stackexchange.com/a/193323
- StavrosK 6y agoI see, thank you. Both your explanation and the link were illuminating.
- simonh 6y agoSound is a more or less coherent propagating oscillation in the medium. A shock wave consists of a very thin front of high entropy propagating through the medium, which is not coherent and essentially disrupts the structure of the medium.
- ummonk 6y agoIf I use a machine to mechanically fling air at, say, 500 m/s, then it will move faster than the speed of sound relative to ambient air, until it gets slowed down and turns into a normal pressure wave.
- glofish 6y agointerestingly even light (in a medium) can travel faster than the speed of light in that medium now both speeds will be slower than the speed of light in vaccum (as that is the highest speed that can be attained) as the light "slows" down from faster speed to its normal speed radiation is emitted https://en.wikipedia.org/wiki/Cherenkov_radiation https://en.wikipedia.org/wiki/Cherenkov_radiation
- refurb 6y agoOK, that was my own ignorance of the fact that "pressure wave" is standard nomenclature. But her comment that ammonium nitrate is a "low explosive" doesn't line up with what I've read.
- KMag 6y agoYes, pure AN is a secondary high explosive with a detonation velocity of 2,700 m//s. The author may be using some shorthand for the detonation shock wave slowing below the speed of sound (and it's pressure front becoming less sharp) as it expands.
- liability 6y agoWikipedia defines 'high explosive' as having a detonation velocity of 3-9 km/s, so by that standard pure AN is not a high explosive, but ANFO is. I'm not sure about AN, but ANFO is a tertiary explosive. But primary/secondary/tertiary is a matter of sensitivity, not detonation velocity.
- vvanders 6y agoLow and high explosives are a very specific thing relating to how they behave in a compressed spaces. If you've ever done model rocketry you're restricted to low explosives for both motors and ejection charges, at least in the US.
- ubercow13 6y agoIs there any source for these definitions? I tried googling low and high explosives on reading this article but I basically couldn’t find anything. One of the only results was this article.
- jmgao 6y agoHere's the ATF definition: https://atf-eregs.18f.gov/diff/555-202/2019-06912/2019-06266?from_version=2019-06266 https://atf-eregs.18f.gov/diff/555-202/2019-06912/2019-06266...