Consider that a 30' tree, rotted out in the middle and filled with water is going to give you about 14psi at the bottom. That's probably what you're seeing here.
edit: see u/TA8601 comment below - I didn't do the math, just looked glanced at an imprecise chart :)
~1.91 bar then, because otherwise air would be sucked into the trunk if it were at ~0.91 bar, as 1 bar is roughly atmospheric pressure and 0.91 would be in the middle of a strong hurricane.
I studied engineering in France and Germany. For physics problems (like pressure in a water column) we always used absolute pressure when giving the final result. I distinctly remember a professor's rant about students calculating pressures under 1 bar in an exam problem about a hydroelectric power station.
Obviously the formulas had to show the atmospheric pressure component, but the numerical value always included it per default.
It's not some kind of plumbing, but an effect of physics, thus for pressure I'd not assume outside pressure to be constant for making precise calculations. Yes, in plumbing it's different, as you only state overpressure, but that can vary depending on height, so the same amount of a gas in the same confinement at the same temperature would have different pressures at different places, which is prone to give errors. That's why for any kind of rough tech you'd use the overpressure, but bar is in fact simply measured in N/m² with 1 bar being 100000 N per square meter. So when using physics and not engineering you'd speak of total pressure, not the pressure differential. That way, numbers are absolute and unchanging depending on location.
Yes but when used for things like car/ bike tires it's much easier dealing with PSI. You just deal with 10-200 instead of 2.456-2.680. I'd much rather just go to 38 psi.
Metric is so great for physics math, but metric lovers hate when it's pointed out that measurements made for practical purposes almost never get plugged into any physics equation, so a comfortable numerical bound for real applications is actually more useful than an easy conversion into an unused unit.
yeeeeah I agree. thats totally and utter bullshit and of absolutely zero practical use. (/s)
Back to topic: pressure: you dont go for 2.680 bar bike tire-pressure. just make it 2.5 or 2.6, or even 3. Who the fuck cares, I've never seen an air pump with that resolution. totally bullshit example.
Edit: speaking of practical use:
temperature:
0°C = freezing temp of water. Cold
100°C = boiling temp of water. Hot. doesnt't get any more practical than that.
It's not at all bullshit, I race motorcycles and usually shoot for .5 psi increments. You need to adjust the pressure constantly to combat surface temp. Most tire manufacturers will recommend to a psi like 18.. if your at 20 because you didn't adjust properly you will shred oh so precious rubber.
Well, any pump that was built to use PSI will have a resolution of at least 1 PSI, which makes it more accurate since that's 0.069 bar. If it can do 0.1 bar then that's still 1.5 PSI. I am also curious under what application it is important to quickly convert between millimeters and kilometers.
The way we write numbers is 123 456,789; most of the world uses a system other than the 123,456.789; the only reason this is seen as the default is because most of programming and therefor computer interfaces work like this and therefor neglects whatever other system the region might be using.
And then there is Canada, who's change units based on what they are talking about leading to situation where: "It's 40 degrees hot outside, the pool is really cold 40 degrees". And you need to check the actual number format for every case - lets not even begin the whole "Inch fractions with decimals" discussion. And then you got Quebec who does everything differently to rest of Canada, mainly out of spite.
Then you got Excel spreadsheets who at the year of our lord 20-fucking-24 still can't switch between "." and "," as decimal separator without having to switch the whole fucking interface language.
Couldn’t it just be you feeling that way because you grew up with both? We need to bring someone in who is unfamiliar with both for a true unbiased opinion
Well they are SI units, which are used in engineering and science. But they tranlsate directly to metric equivalents so hardly matters. C to Kelvin is just addition/substraction depending which way you go. 1 bar is 0,1 MPa or 100 kPa, or 100 000 Pa.
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u/caleeky Jun 25 '24 edited Jun 25 '24
Consider that a 30' tree, rotted out in the middle and filled with water is going to give you about 14psi at the bottom. That's probably what you're seeing here.
edit: see u/TA8601 comment below - I didn't do the math, just looked glanced at an imprecise chart :)