Air pressure inside restaurants
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@abarker said in Air pressure inside restaurants:
Except that the door opens in the same direction whether you are going in or out.
Yeah. I didn't mention this specifically. Did you think you're pushing the door in two different directions, @lucas1?
The primary difference tends to be that traffic going in tends to be around the same time, so pressure within the restaurant doesn't have a chance to differ much from pressure outside. On the other hand, different groups take different amounts of time to eat, so exiting groups are staggered more. As a result, there is often more of a difference between when people are leaving then when they are arriving, so the air pressure difference caused by the kitchen ventilation is more significant as some patrons are leaving.
That actually sounds like a plausible explanation.
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@lucas1 said in Air pressure inside restaurants:
It is a combination of both.
...hence why I suggested putting air pressure on both sides of the paper, so that you could see whether the effect of the air pressure is truly very significant in his experiment.
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@masonwheeler That last explanation was probably a piss take.
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It is beyond the point of the explanation of the complaint tbh.
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@abarker The pressure between the two is irrelevant. It the amount of air you have to move when entering or exiting.
If anyone doesn't believe me just try the door slamming experiment.
If this was an airlock and a space station I wouldn't have an argument.
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@lucas1 said in Air pressure inside restaurants:
Just leave the windows open in your house and let the door go, It will slam hard,.
Only if a breeze catches the door or you have spring hinges on the door.
@lucas1 said in Air pressure inside restaurants:
Shut the windows in your house and let the door go, it won't slam.
Well, if the door slammed in the first example because you had spring hinges, it will still slam here ... because you have spring hinges.
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I dunno what spring hinges are. Probably something American so they doesn't really exist ;-).
Nope, It happens every time (I have a fire door, it is supposed to slam). The door is too light to move enough air to when the windows arent open. It slams hard because it has to move a load of air into the room and it slows down the acceleration so it doesn't slam.
F = ma in action.
The same would happen if you tried opening your car door under water (this is assuming you drove your care into a lake).
Same principle.
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@lucas1 said in Air pressure inside restaurants:
@abarker The pressure between the two is irrelevant. It the amount of air you have to move when entering or exiting.
It is relevant. Here's a little diagram:
Because of the pressure differential, the two regions are attempting to equalize. With the door closed, air cannot pass from the exterior to the interior, creating a force holding the door closed. This is the same principle that makes suction cups work:
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@lucas1 said in Air pressure inside restaurants:
If anyone doesn't believe me just try the door slamming experiment.
OK, I'll bite.
My front door is conveniently oriented at about 90° to the usual wind.
If I leave my front door open, it will stay open.
If I leave my front door open and then open the windows on the upwind side of the house, particularly if I only leave the front door ajar, the door will slam.
If I leave my front door open and then open the windows on the downwind side of my house, or open any windows at all on a day that's flat calm, nothing happens.
It's an airflow thing.
Or have I got you completely wrong on this?
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@lucas1 said in Air pressure inside restaurants:
Nope, It happens every time (I have a fire door, it is supposed to slam).
Fine, ammend my previous statement to include "hydraulic arm" as a possibility. If you have a standard door that isn't configured to close on its own, it won't just slam because your windows are open.
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@tufty Nope it is a combination of both. If the air doesn't move, like in my flat the door won't slam. It you have a large house I suppose it doesn't make as much difference.
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@abarker And it is so small that most people can just put their weight on it and it will open. It is just a little bit more difficult.
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@lucas1 alright look, I tried your experiment. With all the windows in the house closed, I cracked open the door. Then I went and opened a window. The door didn't slam shut. If the batteries in my camera weren't dead right now, I'd show you.
Maybe if a big gust of wind happened to blow through, the door would slam, but that's something completely different from what he was trying to demonstrate, which was the static pressure exerted by the atmosphere. He wasn't trying to demonstrate the power of wind.
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@anotherusername Having read his drivel above, I think lucas is, with his usual level of eptitude, trying to convey a totally different idea.
I think what he's trying to say is that if you swing your door shut, with the windows open it will slam, and with them shut, the slamming will be damped.
Obviously, this is a totally controllable experiment, requiring only an outward-opening front door (I've never seen one of these, but apparently they are a thing in Sweden) and one-way windows that don't allow any wind to flow in when they are open...
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The second time was quite lounder so the door was obviously moving more quickly.
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@tufty hmm, you might be right.
@lucas1 even still, that demonstrates that air pressure increases when it's compressed. Some compression does happen on the side of a moving object that's facing the direction it's moving, but the air can flow around it, so it has somewhere to go. And that force does exhibit itself -- as air resistance -- but it's different from air pressure, which is just the static pressure of the weight of the atmosphere, which is what the video was supposed to show. But actually, it mostly just showed air resistance.
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@tufty Denied mother fucker ... see vid above.
They are obviously a combination of both things mentioned. I mentioned the whole news paper thing as a quick "well look this is what happens when you have something with a lot of force vs a piece of paper".
If you want me to do calculation. I will consider doing them, but considering your attitude publicly and privately on here I am quite hesitant.
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@anotherusername said in Air pressure inside restaurants:
@lucas1 even still, that demonstrates that air pressure increases when it's compressed. Some compression does happen on the side of a moving object that's facing the direction it's moving, but the air can flow around it, so it has somewhere to go. And that force does exhibit itself -- as air resistance -- but it's different from air pressure, which is just the static pressure of the weight of the atmosphere, which is what the video was supposed to show. But actually, it mostly just showed air resistance
They are a function of each other.
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Air resistance is drag, which is a function of fluid density, object area, velocity and reynolds number [edit] and the coefficient of drag of the object, duh.
The density of air is a function of pressure, but for atmospheric air, it's dwarfed by everything else in the equation.
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@tufty That is kinda of right if it is going through a cylinder.
Reynolds number is to do with the "roughness" of what the fluid is flowing through, That "roughness" can be massively increased by bends in an fluid flow.
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Hang on, what happened to the post where you said pressure was irrelevant?
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@tufty Eaten by the edit pencil.
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I said the difference of pressure between the outside and the inside isn't relevant. In this case.
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@Yamikuronue I suppose I just said it better.
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@lucas1 Didja fuck. You said something completely different.
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@tufty He edited his reply to me too, to soften it. I wonder why...
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@Yamikuronue Maybe he's afraid of girls.
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@tufty The thing is when I am talking to you I know I have to be really exact or you will be a bellend over something really trivia. So maybe that is why I did it.
It was so trivial I don't remember doing it.
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@Yamikuronue Because I don't want to be always mean.
I edited a reply because I thought "well that sounds a bit harsh and I didn't mean that maybe I should change it".
Obviously that makes me the worst cunt ever.
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@lucas1 said in Air pressure inside restaurants:
It was so trivial I don't remember doing it.
I'll help:
@lucas1 said in Air pressure inside restaurants:
Reynolds number is to do with the "roughness" of what the fluid is flowing through, That "roughness" can be massively increased by bends in an fluid flow.
That sentence used to be something along the lines of "I've been saying this whole time that air pressure and air density are irrelevant"
@lucas1 said in Air pressure inside restaurants:
I edited a reply because I thought "well that sounds a bit harsh and I didn't mean that maybe I should change it".
I do appreciate the effort.
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@lucas1 only in the sense that they both exist because air has mass.
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@lucas1 said in Air pressure inside restaurants:
you will be a bellend over something really trivia.
No, if that was the case I'd pick you up on your myriad spellar and gramming pismakes. As it is, I'm only picking you up on the fact that you're hopelessly, utterly, wrong.
Anyroadup, I CBA. Did 1000m vertical on this morning's hike, I'm off to bed.
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@Yamikuronue said in Air pressure inside restaurants:
That sentence used to be something along the lines of "I've been saying this whole time that air pressure and air density are irrelevant"
Because I was explaining it in a shit way and I changed it.
Possibly because he will have a go about anything about me given the chance.
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@lucas1 said in Air pressure inside restaurants:
he will have a go about anything about me given the chance.
I'll be honest, I have no sympathy for you there, dude. You do the same thing. You two are a match made in the trolleybus garage.
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@tufty Nope I am not. All you have said so far is "you are a moron".
I said to you if you could show me what was wrong with my thinking I would be genuinely interested.
So far you have been rude and dismissive.
Anyroadup, I CBA. Did 1000m vertical on this morning's hike, I'm off to bed.
Convenient ...
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@lucas1 said in Air pressure inside restaurants:
Convenient ...
Not very. My knees hurt, and I have to service the cars tomorrow.
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@Yamikuronue I'll be honest. I'm not surprised that an SJW would not have sympathy for someone that they disagree with.
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@tufty Whatever mate, last time I tried talking to you your "macbook" needed an update. You can dismiss that for the next thousand years and it wouldn't make you do it. I own 2 macs.
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@tufty if you can jack them up a few feet, the tailpipe's at a more convenient height. You wouldn't have to kneel.
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This is what they do. They act like asshats all the time, piss you off and when you retaliate they make you look like the bad man.
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@Yamikuronue When?
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Is this grammar nazi hour? As long as you can understand what people are saying it doesn't fucking matter. And this is coming from a grammar nazi. It's a very lazy form of arguing, as well.
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@lucas1 said in Air pressure inside restaurants:
This is what they do. They act like asshats all the time, piss you off and when you retaliate they make you look like the bad man.
So a straw-man argument. Look, I knew what he was saying even if all the little dots weren't connected. Fucking thickos.
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@Tsaukpae Probably.
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@masonwheeler said in Air pressure inside restaurants:
What's the deal with air pressure inside restaurants?
I'm sure there's some sort of pressure variation, but it shouldn't be that significant as they don't necessarily want to bar anyone from entering.
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Fuck it I don't care any more.
I had to deal with cunty flaps more than once.
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@tufty Good I like to think that you are in pain. Don't worry I won't get a boner over it.
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@anotherusername said in Air pressure inside restaurants:
@lucas1 now I'm sure that you're just messing with me. That is not what will happen, unless maybe there's a hurricane-force wind blowing directly into your open windows.
But by all means, you go ahead and try it.
To be fair, I don't think it has to be hurricane-force wind. Assuming my apartment is representative, gusts of 30 MPH or so (40% of hurricane force) seem to be enough to slam the lightweight bedroom doors.
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@Dragnslcr Look at the vid I posted.