OK what’s a good instrument to measure air pressure? It has to be pretty accurate and respond quickly. I think the pressure difference inside your mouth is off the scale of a regular barometer.
We can do the experiment by just raising the air pressure on one side. Easy enough to do with a pump. The we measure the force on the hot dog and compare it to the force on something less compressible.
k2dave
Member posted 12-17-1999 05:11 PM
Do you have proof for that claim? Other than “common sense”?
I don’t see how that contradicts my explanation. See below for elaboration.
RM Mentock
Member posted 12-17-1999 05:59 PM
I believe that under normal atmospheric pressure, noodle are pretty darn incompressible.
Huh? It doesn’t deform; it falls apart!
k2dave
Member posted 12-18-1999 05:11 PM
not so sure of the drawn in with the fluid theroy. I would kick around some assumptions to see if we are all on the same playing field
I think that this is the main misunderstanding that’s interfering with you understanding my explanation. The force is not concentrated at the other end of the noodle; it is the result of the flux over the entire noodle. The force that pushes the noodle into your mouth comes from the portion of the noodle that first curves away from your mouth. It is only if the noodle doesn’t curve that the force on the other end of the noodle is the only force on the noodle.
If the noodle later on curves into your wife’s mouth, then the portion that curves away from your mouth will cause a force towards your mouth, while the portion that curves towards your wife’s mouth (or, from her point of view, away from her mouth) causes a force that push the noodle towards her mouth. Net result: part of the noodle moves towards you, another part moves towards your wife. This, of course, assumes that
You and your wife are facing each other.
The noodle isn’t perfectly straight.
If 1) does not hold, then a similar explanation will explain the motion of the noodle. If 2) does not hold, then there will be no portion curving away from you, and the only force will be the pressure of your mouth subtracted from the pressure in your wife’s mouth, and each end of the noodle will move the same way, if at all.
I don’t know if this will help, but consider a noodle like this:
a b c d
----------------
------/ -------------- ----------
-------/<-e f->-----------
If I’ve made the diagram correctly, a and b represnet two mouths. c and d represent bends in the noodle. e and f are the only unopposed forces. If you look at any other force, it will exit the noodle somewhere other than someone’s mouth, and therefore be opposed. Therefore all the noodle left of point b will pushed to the left, and every part right of c will be pushed to the right. The net result will be to straighten the noodle.
Konrad
Member posted 12-18-1999 06:05 PM
I don’t think I’m assuming anything other than no significant compression.
k2dave
Member posted 12-20-1999 06:35 PM
If the noodle bends, then there is cross sectional area.
Scott123
Member posted 12-21-1999 02:30 PM
Exactly! Although I don’t think it was really Cecil that actually said it; it was someone whom Cecil quoted.
RM Mentock
Member posted 12-22-1999 07:33 AM
If you have a pressure differential, and no partition, you’re going to get movement (i.e. wind). I would expect the wind to carry the noodle along.
A few alterations:
RM Mentock
Member posted 12-17-1999 05:59 PM
I believe I have already explained why it won’t, under certain circumstances, buckle. If two opposing forces have the space between them completely filled with noodle, they will be transmitted through the noodle, cancel, and cause no net force and no buckling. Would you care explaining why you think it would buckle, or do you expect us to just take it on faith?
A000b0000000000c0000000d
00000----------------
------/* --------------*----------
-------/<-e00000f->-----------
(The 0’s are because the MB doesn’t seem to like spaces; ignore them.
And another thing to consider: if all forces, even when canceled, cause buckling, why is it that a noodle laying on a plate, with forces cancelling all over the place, doesn’t buckle? Why doesn’t it just fold up under all the pressure?
[. The force is not concentrated at the other end of the noodle; it is the result of the flux over the entire noodle. The force that pushes the noodle into your mouth comes from the portion of the ]
Thats why I said the magnitude of the force, not the actual propellent force. The X-C of the noodle is equal to the X-C at the ends and the interface. I understand what you are saying, and have pondered 2 versions. The 1st is what I assumed you ment. The pressure on the sides acted like a flexable, frictionless tube and the end pressure acted like a piston pressing the noodle through the tube. Then I realized that you ment that any curve that happened closest would impart that force or a component. If so, in my experiment w/ 2 people, we could also hold the noodle in tension, now there was no curve in the noodle, where did the tension force come from?
Also the ‘you can’t push on a rope’ was sort of an enginnering joke in college. we can all see thay you can push a very short rope section but for any decent size rope, no pushing the end is going to make any real difrence at the far end. you might be able to set up some vibration harmonics but you cant expect to actually push anything that way.
No, no. I don’t think it will necessarily buckle, I just don’t think that a limp noodle transmits forces too well. When I place a noodle on straight on the table, and push on the two ends, the noodle buckles. I don’t even have to push very hard.
LOL! I think you should send this question off to Cecil. Make sure you mention that it’s a follow-up.
.
another thought, are noodles ‘pretty darn incompressable’. this was assumed by the fact that a noodle is pretty much waterlogged, and water is basicly incompressable. I am now rethinking that on the following basis:
1 Noodles can accept more water since they can be cooked longer and swell more.
2 noodles exposed to air (taking them out of the pot to put them on the plate) flex and bend. bending creates areas of tension and compression, the starch fibers elongate and compress. water on the compression side has to move either to:
1 a place closer to the fibers, which assumes air in the noodle :. it is compressable
2 that the water just shifts to the other side, which I think is unlikely that the exact amount of water moves to maqintain incompressability.
3 that some water moves (from compression to tension), some leaves the noodle, (in the part of tension), some air enters to make up the diffrence.
if air is present then we can no longer assmun a incompressable noodle.
now for a thought experiment.
lets attach a small rocket engine to a noodle to recreate the propelnt force.
Trial 1
if we put it on the far end and blast off, I say the noodle would obviouslyu buckle and the far end would probally smack me in the face.
Trial 2
If we put it on the close end, inside the mouth and blast off, the noodle pulls in until the rocket hits the inside of my mouth and stopps, I get no more noodle. While the noodle is moving, the outside noodle is acting simularly to the sucking modle, but the inside is clearly not. in this model (rocket on near end)the far end is being pulled, not pushed, the noodle is in tension without concidering air pressure.
Trial 3, if we put the rocket on the interface but this time we install the rocket on a movable track, lets change the rocket to a convayor belt here since it is easier to visualize here (the rocket still works), put a convayor belt above and below the noodle at the interface, and the noodle gets ‘sucked in’, this is the closest to the ‘sucking model’, and helps to demonstrate where forces have to be applied to cause noodle motion.
I think it does buckle. Just so little we don’t notice it easily. A noodle does have some sort of rigidity, just not much. Look at it this way: when you put a noodle in water it never goes perfectly straight, it’s always a bit curvy. Once it starts to curve the rigidity of the noodle balances out the pressure. You might not notice this on a plate because there’s too much friction.
But that is a different explanation than “pressure”. That’s kinda what I’m getting at, and I’m not sure that the wind would carry it along.
Here’s the apparatus we need. An adjustable opening that we can place a noodle in, with a pump (vacuum cleaner?) pumping out the inside. Next to where we’ll place the noodle, we have a pressure guage. Then, for various size openings, we adjust the pump so that the pressure inside is the same at the start for all openings. Then we lay the noodle in the opening. What happens?
[Here’s the apparatus we need. An adjustable opening that we can place a noodle in, with a pump (vacuum cleaner?) pumping out the inside. Next to where we’ll place the noodle, we have a pressure guage. Then, for various size openings, we adjust the pump so that the pressure inside is the same at the start for all openings. Then we lay the noodle in the opening. What happens?
]
here on earth gravity creates friction with the surface. It helps ,I find, to think what would happen in space (no gravity). we do need an atmosphere for this. So lets ask NASA to take a noodle up in the shuttle, when they are about to depressurise the cargo bay doors maby they can place the noodle at the opening and see if it gets blown out.
Unfortunately I am no astronaut, but I have a hunch that that noodle will not just stay there, but move violently away.
But your mouth is not a vacuum. The experiment should duplicate what we’re trying to test. So, maybe lay it in a plate of sauce, and dangle it out of the “mouth”?
It would be much simpler to perform the experiment underwater. Besides, NASA doesn’t have time for real scientific experiments. They’re busy with their little telescope.
The field of noodle-dynamics has been ignored for too long!
I’m confused by all this focus on air pressure differential. If this was the sole or primary cause, wouldn’t it stand to reason that one could, having sucked most of a noodle in, pause for a moment to savor the flavor, then reverse the pressure in the mouth and thereby extrudle the noodle? In other words, what distinguishes sucking from blowing? Or should I be starting a new thread on the ambiguities of fellatio euphemisms?
From RM Mentock:
See my last answer. The noodle doesn’t suck in with an open mouth because of friction between the lips and the noodle, and the ability for the air to rush through the opening rather than requiring it to push on the noodle to open the opening. If the noodle blocks the opening, it gets pushed. If the lips are open a bit, the air can bypass the noodle and enter directly, and the noodle sits limply in the lips. Increase the pressure differential enough to overcome the friction and weight of the noodle hanging out of the mouth, and it would fly in anyway. Like a rapidly decompressing airplane. Put a small opening in the plane skin, and everything not bolted down flies toward the opening to get pushed through until something that cannot be compressed blocks it or the air pressure equalizes. Same diff with the noodle into the mouth. The pressure diff is not large enough to suck the noodle if there is an opening around it, but if there is no opening, the noodle gets pushed into the mouth.
The forces of the air push as close to the opening as possible and still push inward and not be compensated by pushes from inside the mouth. Not pushing on the end, but on the part of the noodle between the lips.
from Konrad:
Konrad, no NASA bashing here. If you must, take it to the pit. (That telescope is real science. Guess what, it’s run by NASA.)
from kjsheehan:
Have you ever tried it? I don’t recall having done so, but in priciple I can’t see why it wouldn’t work to blow the noodle. However, here is the practical problem. When you suck, the lips contract around the noodle, thus ensuring a snug fit and letting no air leak. When you blow, your lips want to pucker outwards away from the noodle, thus letting air slip past and preventing the noodle from moving.
Here is a parallel no one thought of yet - a straw and a spitball. Put the spitball in the straw and blow, and the air pushes the spitball out at high velocity. Put the spitball in the outer end and suck real hard, and see if you get the spitball down your throat. 
IrishMan
Set up the experiment so that the pressure differential is the same, no matter how wide the mouth is. In other words, your vaccuum pump would have to work harder, but the pressure is the same as if your mouth were closed.
.
With all this talk about “sucking”, “lips”, and “lubrication”, I have to go take a cold shower now.
From RM Mentock:
I’m trying to follow you. I think I answered your question.
If the pressure differential is great enough (to overcome friction, weight, etc), the noodle will go into the mouth anyway. (A.k.a. the analogy to a depressurizing airplane.) If the pressure differential is not great enough, the noodle will sit limply on your lips and the air will fill your lungs and you will feel silly having a noodle draped out of your mouth.
If you are making an experiment with an apparatus to simulate the mouth and sucking et al, then you should limit your pump to the capabilities of the lungs/diaphram. If you used elephant lungs attached to a human mouth, you get a different answer. If your pump is large enough, not only does the noodle suck through the opening, but so does the table and the chair and bunsen burner and the lab assistant…
That’s the point:
Is the pressure great enough? That’s why we’d do the experiment. Set the pressure to the same as in a “normal” sucking mouth, and see if it pushes the spaghetti in. At least, that’s the idea. I see many problems with such an experiment…
.
Well, duh, doesn’t seem that complicated to me.
Put a noodle in your mouth. Open your lips a little, so there’s a gap. Suck really hard.
RM, I don’t think the difference between the two cases (lips open vs closed) is in the pressure difference, it is in the positioning of the noodle. As long as there is a gap, the noodle is getting pushed in because it is the weak link. Your cheeks also get sucked in a little, but they only give so far. The noodle moves easier than your cheeks give way. Open the opening, now the friction on the noodle is stronger than the next weakest link - the air already in the opening.
Try this - take someone with a penchant for piercing, and get a good piercing through the lip or cheek - enough to have an air gap. (May take time to grow one if can’t find a suitable candidate already exhibiting this trait. There’s an Indian tribe in the Amazon who have a wooden post through their bottom lip - they would make good candidates.) See if they can suck a noodle. My bet is no. Then plug the hole (duct tape anyone?). Now see if they can suck. Viola. The difference is the air gap is not next to the noodle, but off to the side. Same effect.
If you really want to get serious, do some heavy experimentation on noodle weights, friction coefficients of wet vs. dry noodles, cof of lips (healthy vs chapped, plain vs chapstick). Then calculate the pressure difference required to suck a noodle.
This thread is fun - I can tell you to go suck a noodle and not be offensive.