The power of suction is physically limited.
Someone has never heard of Delta P.
Comment on My ravioli bowl won't unstick. Took about an hour of prying, and still I couldn't unstick the plate.
FreeBeard@slrpnk.net 4 days ago
The power of suction is physically limited. That means it either isn’t suction or op is crazy weak. My guess is that the plastic melted (probably not from boiling Temp) or op is strongly exaggerating.
I_Has_A_Hat@lemmy.world 4 days ago
FreeBeard@slrpnk.net 4 days ago
It’s delta p and not fraction p. The difference between ambient pressure and inner pressure (at least zero) is always smaller than ambient pressure. Delta p is therefore limited.
Earflap@reddthat.com 3 days ago
OK and? A difference of just 2 psi means that a bowl with diameter 4 in. (complete guess) is being held in place with ((4π)=12.562)= 25 lbs of force distributed evenly across the surface of the plate.
A bigger bowl or greater suction changes these numbers dramatically. 2 psi on a 6 in. bowl is held in place with 37 lbs of force. 4 psi on a 6 in. bowl is held in place with 75 lbs of force.
Sure its “limited” in that there can only be a 14.7 pressure difference, but that doesn’t mean anything in terms of “this is really hard to undo”.
And if there’s oil or food or something sealing the gap between bowl and plate… fugheddaboudit.
FreeBeard@slrpnk.net 3 days ago
I sadly don’t understand these units and your point is drained in it. The point I want to make is that the “force” of vacuum is limited by the difference of pressures.
You say it changes “drasticly” with area or suction but that is untrue. It changes linearly with area (not drastically) and pressure difference has a maximum. The maximum is defined by the pressure of the vacuum(=0) and the pressure of the ambient air (1 arm). Both are constant so the maximum is constant and actually not that big.
meekah@lemmy.world 3 days ago
The delta P you’re talking about has much much higher ambient pressure than what is the case here.
And even underwater there is a limit to delta P.
HeyThisIsntTheYMCA@lemmy.world 4 days ago
yeah it’s probably electromagnetic force holding it on there or something
peteyestee@feddit.org 4 days ago
It’s God.
BussyGyatt@feddit.org 4 days ago
Could god microwave a ravioli bowl so hot even he couldn’t pry the plate off the top?
Zentron@lemm.ee 3 days ago
Take that Christians
HeyThisIsntTheYMCA@lemmy.world 3 days ago
How can an ace be one and eleven? What kind of god would do that?
peteyestee@feddit.org 3 days ago
That stuck bowl of ravioli is slowly forming the next dominant species.
FooBarrington@lemmy.world 3 days ago
That bowl and plate are all that keep this reality going
XeroxCool@lemmy.world 4 days ago
How do you figure suction is very limited? You’ve never tried to pull a suction cup straight off, have you? I’m not talking about when suction cups have bad sealing surfaces and slowly leak to the point of popping off or peeling suction cups off from a corner, I’m talking applying it to a good surface and then yanking it.
A shoddy 4.5" suction cup from Harbor Freight is rated at 80lbs carrying capacity for glass, which happens to likely be the same material as the dish (corelle), judging form the thinness. The bowl is probably plastic and had weight on it while these were hot and wet after washing. Please, let me know if you can lift an 80lb dumbell from the end with a single hand with ease.
FreeBeard@slrpnk.net 4 days ago
The difference between ambient pressure and inner pressure is always smaller than ambient pressure. Delta p is therefore limited. The force comes from Delta p times contact area which is constant.
I sadly don’t know your units of mass but as I said a perfect vacuum over an area such as the Bowl is as strong as a muscle. The Ravioli will in no world produce a strong vacuum so muscle will win in most cases.
XeroxCool@lemmy.world 3 days ago
Here, I’ll do metric for you on your theory of muscle being equivalent perfect vacuum. I have some similar corelle dishes. The flat measures 10cm across. That’s 78. 5cm^2 area. Assuming OP lives at sea level, 1atm is 1.033kg/cm^2 which puts the total force at over 81kg. This bowl offers no horizontal surfaces to hook fingers under to utilize geometric advantages and is instead entirely dependent on friciton. If your fingertips can squeeze sideways with enough force to pull a smooth, tapered 81kg object without glue, there’s a gold bar in a Dubai mall with your name on it.
4 inches diameter, 12.6in^2, 180lbs for the Americans.
At some point between 0 and 81kg of force, I’d start worrying about breaking the plate with such little support around the rim. And, as for the impossibility of a perfect vacuum, I’d be easily convinced the bowl could have more than half of the maximum possible pressure differential. A large portion of the interior volume is probably ravioli, minimizing the gas volume. Ravioli are full of water, which means the remainder of gaseous volume in the bowl was probably mostly steam, pushing out the standard air. Steam has an insane compression ratio as it cools and condenses back into water, at about 1700:1. Go watch the video of a tank car imploding from steam condensation.
I cover my bowls the same way. I always cock the plate to the side for this exact reason. My 1L (4 cup) pyrex bowls with silicone lids can cave 1" if they’re allowed to cool for a minute. Steam easily vents from the rim as it’s produced but once it starts cooling, the weight of the lid or plate is plenty to get the initial seal
BullishUtensil@lemmy.world 3 days ago
@FreeBeard separates evacuated Magdeburger hemispheres by hand.
/s
FreeBeard@slrpnk.net 3 days ago
These are 50 cm wide half spheres. If you find that comparable to the situation in the picture your appetite must be enormous.
BullishUtensil@lemmy.world 3 days ago
Rough guess works be 20cm diameter, so 16% of the force required.
And as opposed to the Magdebutger hemispheres, these objects don’t come with handles for good grip.
KillingTimeItself@lemmy.dbzer0.com 3 days ago
it’s a bowl, it’s like trying to pick up a gold bar, how are you meant to get ANY leverage on it without using a knife or something?
arin@lemmy.world 4 days ago
Air pressure is insanely high compared to a vacuum
FreeBeard@slrpnk.net 4 days ago
The pressure acts over the area of contact. For a perfect vacuum it would lead to ~1kN of force. This is the same order of magnitude our muscles produce. If you take into account that the vacuum results from cooling over such a small temperature interval the force can’t be too high.
Hacksaw@lemmy.ca 4 days ago
1kN is equivalent to lifting 100kg… 220lb for our imperial friends… I don’t think I could put that much force on a plate and bowl I was trying not to break
jerkface@lemmy.ca 4 days ago
Your grip on a smooth plastic surface nearly parallel to the force vector you wish to apply is tiny, you cannot exert 1kN in this situation.
Zentron@lemm.ee 3 days ago
Got on to scroll on the clock , wasnt dissapointed