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 Originally Posted by OngBonga
Well, first of all Lara comes home, then Alex half an hour later. Lara tends to open the door more slowly, so my door creaks open slower when she arrives. Alex burts in very quickly, and thus my door opens faster. I normally have my door slightly ajar.
This is all as I suspected.
I wonder if the effect is more pronounced if you have a window open in your room, but no other windows open. I suspect that the random wind from outside will make the internal pressure in your room less well-regulated, and give more variance in the results. I wonder if, assuming the air is still, the door would move more than if the window was closed. Since the pressure increase caused by the shockwave traveling through your doorway will increase the pressure in your room, which would bounce the shock wave back at the door from the other side. This would serve to slow your doors motion, or maybe even cause it to close a little bit, after it opened a little bit. If the window is open, then the pressure difference wouldn't reverse itself as much.
Originally Posted by OngBonga
I thought it was essentially a sound wave. My understanding is that a shock wave that is subsonic is a sound wave, while supersonic shock waves are pressure waves (like when that meteor exploded over Russia and blew out a shit load of windows).
First off, they're all shock waves... and they're all pressure waves. All pressure moves at the speed of sound through a material, because one way of thinking about the speed of sound is the speed at which pressure information propagates through the medium. So it's kinda the definition of sound that it is a pressure wave.
What blew out the windows is the same thing that pushes your door. If your roommates open the doors fast enough, they will blow out your windows (or break the door... structural integrity in question). Same as if you pointed a large speaker at your window and turned it up to 11 (assuming the speaker has the structural integrity to produce a pressure differential strong enough to break the glass before it breaks itself from internal forces).
Also:
There's a mismatch in terms. I said subsonic to mean below the threshold of human hearing, specifically in terms of frequency, as opposed to volume. The shock wave which pushes your door travels at the speed of sound in air.
When you say supersonic, you're probably referring to an object - like a fighter jet - moving through a medium - like air - faster than the speed of sound in that medium.
These are very different uses of the words subsonic and supersonic which are kinda implicitly antonyms. Here, they are not antonyms. They are talking about being below or above very different thresholds which aren't even on the same scale (one is frequency the other is speed).
Importantly, the shock wave created by the meteor over Russia moved at the speed of sound in air. The object creating that shock wave was moving faster than the speed of sound, but the effects of that motion propagate at the speed of sound.
Originally Posted by OngBonga
But this is through a gaseous medium. What happens to a solid that has a supersonic wave going through it? Can it happen?
The wave moves at the speed of sound. The wave itself is not supersonic. That's not possible, as I said above, because the speed of sound is the speed of pressure waves because sound is a pressure wave.
If the solid has another solid move through it above its speed of sound, then problems with definition of solid arise.
Check out Cherenkov Radiation for an example of what happens when a charged particle moves faster than the speed of light through a medium. Recall that the speed of light in vacuum is the cosmic speed limit, but light travels slower through "stuff" than it does through "not stuff" 'cause refractive index.
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