Oops, thats "as long as there’s NO gap…
Another random thought, what’s the difference between sucking a noodle and sucking a pacifier? Someone more recently experienced with pacifiers than I want to comment? I know the pacifier doesn’t slide in while the noodle does, but not sure if the lips open to let air past, or use air through the nasal system to equalize pressure, or what.
Well, pacifiers have a stop.
My “experimental apparatus” would include a pressure guage. Each experiment would be done with the same pressure. So, if you had a hole in your mouth, you’d have to suck harder to maintain the same pressure.
Gotta make sure all experiments are done with the same pressure.
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Here’s some enlightening news. There is confusion here in the perception of “vacuum” as well as “pressure” vs. “velocity”. There is an entire field devoted to this concept known as pneumatic conveying.
First, the vacuum created by a human is very slight. By no means can the mouth or lungs reach full vacuum conditions. If we could, there’d be complications. The vacuum one can create is better referred to as a partial vacuum. In this case, just below atmospheric - a slight differential perhaps measured in small units known as inches of water column (in wc). (Note: 1 psi = 27.71 in wc)
Both your vacuum cleaner at home and also factories handling dried solids (powders, etc.) use different forms of pneumantic conveying to “pull” or “push” solids around - like the spaghetti. (Note: “pull” or “push” is the jargon used to describe the design of the pneumatic system relative to the position of the blower.)
All these systems use a small blower, typ. just a fan, which creates only a small differential in pressure; YET, a high enough velocity to entrain the solids.
Do our cheeks realy bow in under vacuum? Not really…it’s more our muscles as we start out from a natural, puckered position. As noted, you cannot push on a rope, and the limp spaghetti noodle is not really being pushed by air pressure.
So, it is the velocity of the incoming air rushing into the mouth very near the lips that takes the spaghetti along for the ride.
And, it’s only a small pressure differential at work here to motivate the air.
Hope this helps - bon appetit!
I’d rather have a bottle in front of me than a frontal lobotomy - Hawkeye 4077th
I just had a new thought. Anyone tried sucking two or three noodles simultaneously? I figure that would eliminate the idea that the lips are creating a perfect seal.
In light of Jinx’s comments I once again renew my plea for someone to find a feasable way to test the air pressure inside the mouth when sucking.
k2dave Member posted 12-22-1999 10:25 PM
This was your most coherent statement. Did you just assume that there was tension, or did you actually measure tension? And are you sure it was completely straight?
Konrad
Member posted 12-23-1999 12:25 PM
But why do all these phenomenon occur when the noodle is on the plate, but not when the noodle is in the air? Remember, sucking subtracts, not adds, pressure. If pressure were to cause a sucked noodle to buckle, then it must cause a stationary noodle to buckle. The fact is, canceled forces don’t cause noodle to buckle.
kjsheehan
Member posted 12-30-1999 09:58 AM
Three possible answers, in order of decreasing confidence:
You can blow out a noodle.
There is more friction in your mouth. To blow the noodle out of your mouth, you push the noodle horizontally. When you suck the noodle, the motion is vertical. There is much more horizontal friction than vertical friction.
Humans can create more of a pressure differential sucking than blowing.
Jinx
Member posted 01-05-2000 07:18 AM
I’m really not convinced by this possibility. I mean, compare the mass of the air that is supposedly going past with the mass of the noodle. You expect me to believe that that little air can drag along several grams of noodle?
Jinx!
Nice post. Where you been? We coulda used you.
As I understand your explanation though, it seems to go against Cecil’s at http://www.straightdope.com/classics/a4_184.html . It seems to be along the same lines as the one he first thought of (and immediately rejected)–see my post to this thread 12-18-1999 10:48 AM.
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RM Mentock asked “Where have I been?” Missing out, no doubt! (Hey, has Cecil seen my TV remote?)
I will see if I can dig up more details on entraining velocities in relation the mass of an object. This will shed light on the general issues involved. (Frequently, this data might be given as a mass flow rate or a volumtric flow rate at standard conditions (usu. 60 F, 14.7 psia).
Meanwhile, if someone has their own pasta maker, they could make longer and longer strands (record the weights) and inhale.
Repeat until inhaling will not lift the strand! (Individual results may vary.)
As a crude model, some empirical data IS known in the field from medical and scuba.
(Although scuba settings would require some adjustments for very, very shallow diving?)
Some insight might be gained from people who work with portable oxygen equipment. Some tanks have two gauges to tell you the pressure downstream of the regulator…as well as the pressure in the tank. This will give us a feel for lung pressure (plus minimal line losses).
Also, people who work with asthma patients probably are aware of some healthy range of volumetric flowrates (based on the average set of lungs). This can tell us just how fast the air is moving under suction with normal breathing.
I’ll spare the details of how one could model one’s pucker as a restricting orifice first without and then with spaghetti in place.
(And the mechanics of sneezing would probably blow us all away!)
Let me see what I can dig up as far as useful data ASAP.
G’zunt-heit!
I’d rather have a bottle in front of me than a frontal lobotomy - Hawkeye 4077th
Jinx
Member posted 01-06-2000 07:44 AM
It seems to me that what is relevant is not the weight of the entire noodle but the weight of the portion of the noodle not supported by the plate.
All this talk of the noodle buckling doesn’t make any sense. Did anyone ever notice that you can push water using pressure without it buckling (i.e. sucking it up through a straw in a glass)? Water is hardly more rigid than a wet noodle.
The reason the water doesn’t buckle (even though the surface may ripple due to other forces) is that the pressure is uniform on all the externally exposed surfaces.
And that’s why the noodle doesn’t buckle too.
Difference between water in a straw and a noodle: the straw performs the function of the side of the noodle, and keeps the water constrained. A noodle does not have a straw, and relies on the surface tension (cohesion, structural integrity et al) to keep it from buckling. Notice that when the water exits the straw in the mouth it falls apart just like liquids are expected to, but the noodle does not (unless it’s really soggy) and retains it’s structural integrity.
The noodle doesn’t buckle because it has a structural integrity and can withstand the stresses.
Because other factors are pulling the noodle into the mouth. Since it’s getting pulled it’s also getting straightened out.
galt: Water can’t buckle because it’s not easily compressible. And also because it’s not a solid. How could a liquid buckle?
The water column is a bad example, and the behavior of a column of fluid is outside our scope. In short, the water column cannot model the behavior of the noodle.
About pneumatic conveying, I did find comment that we breathe in about 3500 gallons of air per breath. And, that’s under a relaxed state. A breath is just a matter of seconds, I’d wager, so the velocities must be high.
In a preliminary search on pneumatic conveying literature, I did confirm that a small pressure differential is all that is needed to develop entraining velocities. But, I will see if I can find a chart of some kind bringing mass into the picture.
As for my suggested experiment with the pasta maker, “The Ryan’s” comment is noted. But, the various lengths of spaghetti strands would reveal the threshold mass at which the spaghetti could no longer be entrained. Of course, there is a wide margin of error, but it’s a crude way to get at this value.
I am still working on the empirical data. More details to come ASAP.
The scary thing is that 90% of the people think they’re above average! - unknown
Jinx
Member posted 01-11-2000 07:43 AM
About pneumatic conveying, I did find comment that we breathe in about 3500 gallons of air per breath.
Would you like to revise that number by a few orders of magnitude?
Yeah, just wanted to see if you were awake.
I will have to find a more reliable source. That was just a quick-stat I found when viewing other questions on the message boards about breathing.
Thought it would make interesting fodder.
Sorry, I didn’t mean to imply that the column of water in a drinking straw is analogous to the noodle being pushed on by air. The column in the straw is analogous to the parts of the noodle between your lips, and is irrelevant for my point. The part which is analogous to the noodle is the body of water laying in the puddle. The sides of the noodle which are exposed to the 1 ATM air have no more reason to buckle than the surface of your puddle has reason to buckle. It’s all at equal pressure.
In fact, treat the water as the degenerative case of the really mushy noodle. The same forces draw the noodle in as the water, but the noodle isn’t as able to deform as the water.
As promised from a prior posting, I have gathered some data on the lungs and pneumatic conveying as well. Let me run through some calcs, and I will have some data to post ASAP! Thanks for being patient!
Ok, in defense of my pneumatic conveying explanation, here’s the data I promised: The lungs of a 150-lb human have an average tidal flow rate of 5.0 liters per hour. Tidal flow is basically normal breathing. Converting to English units, this equates to 0.18 ft^3/hr or 3e-3 ft^3/min.
Next, unsing my micrometer, I found the diameter of a #9 spaghetti strand to be 1/16" (uncooked), and I assumed it be 1/8" upon cooking. This is a ballbark figure which is not unreasonable. Then, I assumed my pucker has a diameter of 1/4". Finally, I determined the available area through which air is inhaled across the lips. The total area of my pucker minus the cooked spaghetti left 2.56e-4 ft^2 open space. Ok, this assumes an annulus of open space, but you’ll soon see how this is a trivial point.
Next, knowing volumetric flow rate is the scalar product of velocity times area, we can determine the average velocity of inhaled air: Qdot = vA. solving for v, w find v = 11.7 ft/min or about 700 ft/hr. (Note: Qdot means vol. flow per unit time)
Ok, if you argue the free space in my pucker’s “annulus” is actually less, then I say the velocity could be even higher since area is in the denominator when solving for velocity. You’ll recall that a smaller denominator yields a larger solution.
Finally, a handbook on pneumatic conveying says that low velocities of 500-1000 ft/hr yield a type of conveyance that does not totally entrain the mass. In other words, the mass may rest against the wall(s) of a channel (my lips) and still be “sucked in”.
Beyond this, I have come to find the body can do something surprising. While recently sucking on a straw to enjoy a thick shake, I discovered I could breathe normally through my nose yet still create a partial vacuum in my mouth itself…“pulling up” the shake into the mouth (without swallowing). This shouldn’t be, and it indicates there may be some valving in the anatomy permitting this.
Well, in closing, all I can say is that while a small differential in air pressure may motivate the air, we are often observing the supplemental effects of velocity - not just dP. Also, pneumatic conveying literature I have access to mentions that small dP (changes in pressure) can yield relatively high velocities. If not for this fact, pneumatic conveying and probably your vacuum cleaner would not be successful working strictly by dP.
We might never lay this subject entirely to rest, but pneumatic conveying is quite a motivating “force”.
It’s lunchtime…hankering for spaghetti!
Ok, in defense of my pneumatic conveying explanation, here’s the data I promised: The lungs of a 150-lb human have an average tidal flow rate of 5.0 liters per hour. Tidal flow is basically normal breathing. Converting to English units, this equates to 0.18 ft^3/hr or 3e-3 ft^3/min.
Next, unsing my micrometer, I found the diameter of a #9 spaghetti strand to be 1/16" (uncooked), and I assumed it be 1/8" upon cooking. This is a ballbark figure which is not unreasonable. Then, I assumed my pucker has a diameter of 1/4". Finally, I determined the available area through which air is inhaled across the lips. The total area of my pucker minus the cooked spaghetti left 2.56e-4 ft^2 open space. Ok, this assumes an annulus of open space, but you’ll soon see how this is a trivial point.
Next, knowing volumetric flow rate is the scalar product of velocity times area, we can determine the average velocity of inhaled air: Qdot = vA. solving for v, w find v = 11.7 ft/min or about 700 ft/hr. (Note: Qdot means vol. flow per unit time)
Ok, if you argue the free space in my pucker’s “annulus” is actually less, then I say the velocity could be even higher since area is in the denominator when solving for velocity. You’ll recall that a smaller denominator yields a larger solution.
Finally, a handbook on pneumatic conveying says that low velocities of 500-1000 ft/hr yield a type of conveyance that does not totally entrain the mass. In other words, the mass may rest against the wall(s) of a channel (my lips) and still be “sucked in”.
Beyond this, I have come to find the body can do something surprising. While recently sucking on a straw to enjoy a thick shake, I discovered I could breathe normally through my nose yet still create a partial vacuum in my mouth itself…“pulling up” the shake into the mouth (without swallowing). This shouldn’t be, and it indicates there may be some valving in the anatomy permitting this.
Well, in closing, all I can say is that while a small differential in air pressure may motivate the air, we are often observing the supplemental effects of velocity - not just dP. Also, pneumatic conveying literature I have access to mentions that small dP (changes in pressure) can yield relatively high velocities. If not for this fact, pneumatic conveying and probably your vacuum cleaner would not be successful working strictly by dP.
We might never lay this subject entirely to rest, but pneumatic conveying is quite a motivating “force”.
It’s lunchtime…hankering for spaghetti!