Vacuum or pressure to move spaghetti through a hole

[houlahound]

I'm impressed, but I see nowhere in the equation the optimal cooking time for spaghetti at STP??

 

[Chestermiller]

I'm impressed, but I see nowhere in the equation the optimal cooking time for spaghetti at STP??

I always use 10 minutes.

 

[houlahound]

Cheers thanks, I have one further question;

1. Does this have anything to do with string theory.

and

2. If in space nobody can hear you scream, can you still slurp spaghetti as ∆P < 0.

 

[Chestermiller]

Cheers thanks, I have one further question;

1. Does this have anything to do with string theory.

and

2. If in space nobody can hear you scream, can you still slurp spaghetti as ∆P < 0.

You're making me hungry.

 

[Low-Q]

The present hydrodynamic lubrication model recognizes the fact that the most important physical mechanism responsible for the noodle being sucked through the lips and into the mouth is provided by the viscous drag and pressure flow of the fluid in the annular gap between the lips and noodle. When the liquid advances axially through the gap, it drags fluid with it. Additional fluid flow is provided by the pressure difference between air outside and the air inside the mouth. Both these components of the fluid flow contribute to the axial shear force on the surface of the noodle. The model takes all this into account.

Will the same force be applied to a stiff short steel rod - if the rod is lubricated with tomato sauce first? Or is it more forces applied to suck that rod into the mouth - such as surface pressure on the rods flat end?
The rod will stop moving when the end inside the mouth hits something, but the spagetti will not stop due to its flexible nature.

 

[Chestermiller]

Will the same force be applied to a stiff short steel rod - if the rod is lubricated with tomato sauce first? Or is it more forces applied to suck that rod into the mouth - such as surface pressure on the rods flat end?
The rod will stop moving when the end inside the mouth hits something, but the spagetti will not stop due to its flexible nature.

The effect of the pressure on the rod's flat end will be negligible. So the force on a noodle and on a rod will be about the same (assuming they are both being held manually outside the mouth by applied tension).

 

[jbriggs444]

The effect of the pressure on the rod's flat end will be negligible. So the force on a noodle and on a rod will be about the same (assuming they are both being held manually outside the mouth by applied tension).

I am not following this. As I understand your contention, the pressure difference on a thin ring of air surrounding a rod passing through the lips is sufficient to propel both air and rod into the mouth, but the pressure difference on a thick cylinder is inadequate to do so.

 

[Chestermiller]

I am not following this. As I understand your contention, the pressure difference on a thin ring of air surrounding a rod passing through the lips is sufficient to propel both air and rod into the mouth, but the pressure difference on a thick cylinder is inadequate to do so.

Perhaps I spoke too hastily. But, in any event, the case of a relatively short rigid rod is certainly much different from a long flexible noodle, especially if the rigid rod has its end cut off while the noodle is much longer, curved, and can not capitalize on the free end pressure pointing directly into the person's mouth. My formal background is in fluid mechanics, and I've had lots of experience with lubrication flow. I am very confident that it is viscous shear and pressure flow in the narrow gap between the lips and the noodle that is responsible for the noodle suction effect.

 

[jbriggs444]

can not capitalize on the free end pressure pointing directly into the person's mouth.

If the noodle is stationary then the portion not pointing directly into the mouth is irrelevant and there is still a net pressure surplus on the side facing directly away from the mouth. If the noodle is in motion then centripetal acceleration is required, but that means that the noodle is already in motion as a result of the pressure differential.

 

[Stephen Tashi]

I am very confident that it is viscous shear and pressure flow in the narrow gap between the lips and the noodle that is responsible for the noodle suction effect.

People who have an attraction to classical mechanics will find it more attractive to explain the situation without using fluid flow. Can we think of an experiment that would highlight the critical role of pressure flow?

Suppose I imagine a cylinder partially inserted into a chamber so one end of the cylinder rests on the flat floor of the chamber (allowing no air between that end of the cylinder and the floor). The other end of the cylinder is outside the chamber. The cylinder passes through a round hole in the top of the chamber that allows no air between the sides of the hole and the cylinder. An explosive charge is set off in the chamber. Does classical mechanics predict the cylinder will be blown out of the chamber? I think the mechanics of rigid bodies doesn't predict any difference between the behavior of such a cylinder and the behavior of a cylindrical column that was cast as an integral part of the chamber.

 

[Chestermiller]

If the noodle is stationary then the portion not pointing directly into the mouth is irrelevant and there is still a net pressure surplus on the side facing directly away from the mouth. If the noodle is in motion then centripetal acceleration is required, but that means that the noodle is already in motion as a result of the pressure differential.

Are you saying that you are not willing to accept a fluid mechanics explanation of what is happening?

 

[Chestermiller]

People who have an attraction to classical mechanics will find it more attractive to explain the situation without using fluid flow. Can we think of an experiment that would highlight the critical role of pressure flow?

Suppose I imagine a cylinder partially inserted into a chamber so one end of the cylinder rests on the flat floor of the chamber (allowing no air between that end of the cylinder and the floor). The other end of the cylinder is outside the chamber. The cylinder passes through a round hole in the top of the chamber that allows no air between the sides of the hole and the cylinder. An explosive charge is set off in the chamber. Does classical mechanics predict the cylinder will be blown out of the chamber? I think the mechanics of rigid bodies doesn't predict any difference between the behavior of such a cylinder and the behavior of a cylindrical column that was cast as an integral part of the chamber.

Can you please provide a diagram?

 

[jbriggs444]

Are you saying that you are not willing to accept a fluid mechanics explanation of what is happening?

I have seen no supporting reasoning for the mechanism that you have offered. So no, I do not accept it.

 

[Chestermiller]

I have seen no supporting reasoning for the mechanism that you have offered. So no, I do not accept it.

What would it take to convince you? The. derivation of the basic equations? The solution to the equations? Or what?

 

[jbriggs444]

What would it take to convince you? The. derivation of the basic equations? The solution to the equations? Or what?

You are crediting viscous sheer stress from air tangent to the spaghetti strand for providing the inward impetus into the mouth. I want to see a second law analysis on the air to justify such a claim.

The inward impetus on the air (pressure difference times cross-sectional area of the annulus) must be at least equal to the impetus that it is able to transmit to the spaghetti strand. But the spaghetti strand is also subject to the same pressure difference and has a cross-sectional area larger than that of the annulus of air.

Accordingly, it seems clear that the primary inward impetus on the spaghetti is direct atmospheric pressure and not lateral viscous friction.

 

[Chestermiller]

You are crediting viscous sheer stress from air tangent to the spaghetti strand for providing the inward impetus into the mouth. I want to see a second law analysis on the air to justify such a claim.

The inward impetus on the air (pressure difference times cross-sectional area of the annulus) must be at least equal to the impetus that it is able to transmit to the spaghetti strand. But the spaghetti strand is also subject to the same pressure difference and has a cross-sectional area larger than that of the annulus of air.

Accordingly, it seems clear that the primary inward impetus on the spaghetti is direct atmospheric pressure and not lateral viscous friction.

See the following quote about pushing on a wet noodle from the link https://en.wikipedia.org/wiki/Wet_noodle:

(pushing on a wet noodle is) An example of unproductive action, because pushing an actual wet noodle, as opposed to pulling it, accomplishes nothing.[3][4] George S. Patton is said to have used a wet noodle on a plate to demonstrate an aphorism on the need for leadership, saying "Gentlemen, you don't push the noodle, you pull it."[5]

I hope you're not trying to push on a wet noodle.

I'm going to work on a model of the problem you have in mind. This model will assume that there is no drag on the noodle by the lips (no friction). I will estimate the tension variation along the noodle, and then examine the stability problem related to the noodle tendency to buckle if the pressure outside pushes on the noodle. I'll report back.

 

[Chestermiller]

@jbriggs444 If you liked my previous post, you are going to like this one even more. I have finally seen that what you have been saying is correct.

The easiest way to model this is to evaluate it in terms of gauge pressures, rather than absolute pressures (this is permitted because compressibility effects can be neglected). Even if the noodle is curved over the front contour of your lower lip and dangling down, the gauge pressure at the very bottom of the noodle is zero, and the gauge pressure normal to the noodle surface (outside your mouth) is also zero. So, in terms of gauge pressures, the only tangential forces acting on the noodle are the tension created by vacuum inside your mouth and the tangential component of gravity away from your mouth. If you apply enough vacuum within your mouth, it will be sufficient to overcome the gravitational force, and the noodle can be sucked in. That is, the tangential forces are tensile and balanced. This is almost the same thing as sucking in a liquid through a straw (or even better, a crazy straw).

The noodle will not buckle because, in terms of gauge pressures, the noodle is under tension over its entire length. It is being pulled into your mouth, rather than being pushed. From the standpoint of absolute pressures, the absolute pressures normal to the surface of the noodle stabilize it even though, in terms of absolute pressures, it is being pushed and is under absolute compression in the tangential direction. I hope the latter makes sense.

I now also see that the hydrodynamic lubrication mechanism I described, while present, is secondary.

Chet

 

[jbriggs444]

Thank you, Chet. I'd been wracking my brain trying to figure out if there was some subtle angle that I'd been missing.

 

[Nidum]

Tie the outboard end of the spaghetti strand to a fixed anchor point .

Have the strand nominally horizontal but sagging loose .

When you attempt to ingest the strand in the normal way what happens ?

 

[Stephen Tashi]

The effect of the pressure on the rod's flat end will be negligible. So the force on a noodle and on a rod will be about the same (assuming they are both being held manually outside the mouth by applied tension).

Taking the viewpoint of the original post, the "pressure" is the result of forces perpendicular to the walls of the rod, so if the rod is horizontal and we neglect or eliminate the pressure on end of the rod that is outside of the mouth, then how do these vectors produce a net force in the direction of the mouth?

 

[Chestermiller]

Taking the viewpoint of the original post, the "pressure" is the result of forces perpendicular to the walls of the rod, so if the rod is horizontal and we neglect or eliminate the pressure on end of the rod that is outside of the mouth, then how do these vectors produce a net force in the direction of the mouth?

This was addressed in a subsequent post.

 

[Stephen Tashi]

This was addressed in a subsequent post.

Are you referring to post #43 ?

 

[Chestermiller]

Are you referring to post #43 ?

No. Post #52

 

[Stephen Tashi]

No. Post #52

That post is talking about the noodle instead of the rod, but I anticipate the answer for the rod would also attribute the net force to "the tension created by the vacuum inside your mouth". However, the original post is ( I think) about how to understand the forces as vectors Why does the vacuum inside the mouth exert a net "pull" on the end of the rod?

In order for "the vacuum" to exert a net force on the rod, the pressure outside the mouth must be greater than the pressure inside. But if we view the pressure outside the mouth as caused by discrete force vectors acting (only) perpendicular to the sides of the rod then why does the pressure on the outside to the rod have any effect on a force acting along the length of the rod - i.e. as far as force along the length of the rod goes, why should "pressure" on walls of the rod have any more effect than a "vacuum" would upon those walls?

I think an explanation involves the fact that "pressure" on a surface has different results than a force vector normal to that surface. Can we say that "pressure" exerts "a force in all directions"?

 

[Chestermiller]

That post is talking about the noodle instead of the rod, but I anticipate the answer for the rod would also attribute the net force to "the tension created by the vacuum inside your mouth". However, the original post is ( I think) about how to understand the forces as vectors Why does the vacuum inside the mouth exert a net "pull" on the end of the rod?

In order for "the vacuum" to exert a net force on the rod, the pressure outside the mouth must be greater than the pressure inside. But if we view the pressure outside the mouth as caused by discrete force vectors acting (only) perpendicular to the sides of the rod then why does the pressure on the outside to the rod have any effect on a force acting along the length of the rod - i.e. as far as force along the length of the rod goes, why should "pressure" on walls of the rod have any more effect than a "vacuum" would upon those walls?

I think an explanation involves the fact that "pressure" on a surface has different results than a force vector normal to that surface. Can we say that "pressure" exerts "a force in all directions"?

You're correct that the pressure forces normal to the cylindrical surfaces of the noodle don't affect things. It is only the pressure forces on the free ends that play a role. These are related to tangential tensile forces within the noodle. The difference between these forces on the ends support the gravitational component of tangential force along the noodle, and also provide any tangential acceleration along the tangential contour of the noodle. The noodle basically has a varying tangential tension along its length. Post #52 shows that the problem can be analyzed more easily in terms of gauge pressures and associated tensile forces. Think of a noodle hanging in tension under its own weight as a first step in the thought process.

 

[Stephen Tashi]

You're correct that the pressure forces normal to the cylindrical surfaces of the noodle don't affect things. It is only the pressure forces on the free ends that play a role.

I like your fluid mechanics explanation better than that!

As you indicated in another post, the small area of the free ends makes the net forces on them negligible.

We can think of the rod as a piece of uncooked spaghetti. Suppose the free end of the spaghetti that is outside the person's mouth is pressed against a wall so there is no air between it and and the wall. There is no air pressure on that end. Will the person be able to suck the spaghetti into his mouth? (I don't claim to know.)

 

[jbriggs444]

As you indicated in another post, the small area of the free ends makes the net forces on them negligible.

Of course, that is wrong. The pressure differential multiplied by the cross section of the noodle is the net force that applies.

On the case of a strand of uncooked spaghetti end-on to the wall, that does not seem realistic. One does not generally see flat polished ends on spaghetti strands make airtight seals with walls.

 

[Stephen Tashi]

Of course, that is wrong. The pressure differential multiplied by the cross section of the noodle is the net force that applies.

The question in the original post asks why something like that should be the case. For example, in the case of a cylindrical rod, if we analyze the rod with a "free body" diagram, where do we draw the force vectors and how do we explain their causes?

On the case of a strand of uncooked spaghetti end-on to the wall, that does not seem realistic. One does not generally see flat polished ends on spaghetti strands make airtight seals with walls.

I agree. But the situation is interesting as a thought experiment for inquiring what elementary mechanics predicts. It seems to me that the effects of "pressure" aren't easily analyzed as set of vectors. In the idealized world of elementary mechanics the wall would not exert a force on the end of the stick of uncooked spaghetti unless there was a "reaction" force that arose because some some other force pushed the spaghetti toward the wall. Would the "pressure differential" between the two ends of the stick be zero?

 

[Andy Resnick]

It seems to me that the effects of "pressure" aren't easily analyzed as set of vectors.

Well that's just it, isn't it? Pressure is the isotropic part of the stress tensor. Stress is a tensor quantity that expresses more than just pressure. Shear stress can't easily be formulated in terms of a vector- at least not in any useful way.

https://en.wikipedia.org/wiki/Cauchy_stress_tensor

 

[Chestermiller]

Over the past several days, I have spent lots of time thinking about this problem, and I would like to present what I have come up with. My focus has been on addressing the questions that @Stephen Tashi has been asking, and on using a solid mechanics approach of the type that @Andy Resnick has been recommending.

The analysis considers a cooked spaghetti noodle, and neglects its bending stiffness; so it is treated as being very flexible. The component of the gravitational force perpendicular to the noodle axis is neglected, but the component of the gravitational force tangent to the noodle contour is included. So the stresses in the noodle do not vary over its cross section. The force balance on the noodle is confined to consideration only of the tension and stress variations in the direction tangent to the noodle contour.

The principal stresses are locally approximated as being oriented in the tangential (axial) direction $\sigma_z$, the radial direction $\sigma_r$, and the hoop direction $\sigma_{\theta}$. We employ Hooke's law in 3D to describe the deformational behavior of the noodle material, and to analyze the state of stress and strain in the noodle:$$\epsilon_z=\frac{\sigma_z-\nu(\sigma_r+\sigma_{\theta})}{E}$$
$$\epsilon_r=\frac{\sigma_r-\nu(\sigma_z+\sigma_{\theta})}{E}$$
$$\epsilon_{\theta}=\frac{\sigma_{\theta}-\nu(\sigma_r+\sigma_{z})}{E}$$where $\nu$ is the Poisson ratio and E is the Young's modulus. In our system, because of cross sectional symmetry, the cross sectional stress distribution will be transversely isotropic, such that $$\sigma_{\theta}=\sigma_r$$ and $$\epsilon_{\theta}=\epsilon_r$$ This enables us to eliminate the hoop stress and hoop strain from the analysis to obtain:
$$\epsilon_z=\frac{\sigma_z-2\nu\sigma_r}{E}$$
$$\epsilon_r=\frac{(1-\nu)\sigma_r-\nu\sigma_z}{E}$$

I've used the following diagram to analyze the problem:

The room atmospheric pressure outside the mouth is $P_a$, and the reduced pressure inside the mouth is $P_v<P_a$. So the pressure difference $P_a-P_v$ supports the component of the noodle weight tangent to the noodle contour.

Four sections of the noodle are identified in the figure. Section AB is entirely within the mouth, and does not support any weight; the pressure acting on the surface of the noodle is isotropic and uniform at $P_v$ in this section. Section DE is outside the mouth and is oriented vertically; the tension in the noodle varies axially in this region, although the pressure on the external noodle surface does not vary from $P_a$. Section CD is also outside the mouth, and is contact with the lower lip (but not the upper lip); so the contour is curved, and only a fraction of gravitational force acts tangent to the contour. In section BC, the noodle is in contact with both lips, and the pressure on the noodle surface varies from $P_a$ at location C to $P_v$ at location B.

I think I'll stop here for now and continue in my next post. Please let me know if you prefer for me to analyze this problem in terms of absolute pressure and stresses, or in terms of absolute pressures and stresses.

Chet

 

[Stephen Tashi]

My personal preference is that you first analyze the simpler case of horizontal rigid rod (an uncooked stick of spaghetti). I suspect that if we try to represent "pressure" as family of arrows that push against the rod perpendicular to its surface then we must assume that the vertical surfaces at both ends of the rod are exposed to pressure in order to arrive at a component of force in the horizontal direction.

If we have a curved piece of spaghetti or a curved rod then forces perpendicular to its curved surface can have horizontal components. In that case, it is not mysterious that "pressure" can exert forces that push the rod into the mouth.

Your analysis takes for granted that the pressure differential produces a horizontal component of force. I believe it does, but my interpretation is that the original post is asking for an explanation of how it produces a horizontal component of force.

It's amusing (and perhaps a choking hazard) to consider a variation on the problem. Physics labs usually have sets of cylindrical brass weights. Suppose "the class clown" experiments with the weights by trying to suspend them off the ground by sucking on them. He looks directly down at the floor and, with the weight in his mouth, he sucks on it to keep the weight from falling. Then he tries the experiment on other objects - pieces of string, pencils, lengths of copper wire etc.

I wonder if the results such experiments would agree with calculations based on elementary mechanics. More weight would make things harder to suspend, more cross sectional area would make them easier to suspend. The trade-off between these aspects could be studied. For example, what is the longest length of bare #14 copper wire that the class clown can suspend by sucking on it?

Class clowns often outwit simple models. We might have to resort to your viscous flow model to explain things.

 

[Chestermiller]

My personal preference is that you first analyze the simpler case of horizontal rigid rod (an uncooked stick of spaghetti). I suspect that if we try to represent "pressure" as family of arrows that push against the rod perpendicular to its surface then we must assume that the vertical surfaces at both ends of the rod are exposed to pressure in order to arrive at a component of force in the horizontal direction.

If we have a curved piece of spaghetti or a curved rod then forces perpendicular to its curved surface can have horizontal components. In that case, it is not mysterious that "pressure" can exert forces that push the rod into the mouth.

Your analysis takes for granted that the pressure differential produces a horizontal component of force. I believe it does, but my interpretation is that the original post is asking for an explanation of how it produces a horizontal component of force.

I'm going to take your advice, and first analyze a horizontal rigid rod. Then I'll move to a model of a vertical rigid rod. Then finally I'll model a flaccid spaghetti noodle.

First let's consider the case of a stationary horizontal rigid rod held in place by your lips.

In this case, no pressure differential is required between your mouth and the outside atmosphere. Your lips must merely apply an upward force to the rod to balance its weight (not shown in the figure), and they must also apply a moment to the rod (shown in orange as a couple) to prevent it from rotating.

Let's next consider the case of a horizontal rod advancing into your mouth with velocity V.

In this case, a pressure differential is required to balance the viscous shear stress between your lips and the rod, given by Newton's law of viscosity: $$\tau=\eta\frac{V}{h}$$where $\eta$ is the fluid viscosity in the annular gap and h is the annular gap opening. The pressure difference is related to the shear stress by:$$(P_A-P_V)\pi r^2=2\pi r L\tau$$where r is the radius of the rod and L is the length of contact of the rod with your lips. So, combining these two equations, we get:$$(P_A-P_V)=\eta\frac{2 L}{r}\frac{V}{h}$$ (There is a additional air flow between the outside atmosphere and the mouth required to sustain the pressure differential, i.e., to provide the seal, but this air flow is small)

In the case where there is a pressure differential, note that the two ends of the rod do not have to be flat. Even if the ends are rounded, the net pressure force is still $(P_A-P_V)\pi r^2$.

Comments about the horizontal rigid rod case?

 

[Andy Resnick]

The room atmospheric pressure outside the mouth is $P_a$, and the reduced pressure inside the mouth is $P_v<P_a$. So the pressure difference $P_a-P_v$ supports the component of the noodle weight tangent to the noodle contour.

I think this is the wrong approach- the fluid flow around the spaghetti is the essential part, not any solid-body mechanics. The pressure difference generates fluid flow through the annulus; this fluid flow is what generates sufficient shear stress to draw in the noodle (uncooked or not). The problem should first be simplified by 'looking down'- this reduces the problem to an axisymmetric 2-D velocity profile with coordinates (r,z). The z-direction flow velocity in the annulus can be approximated in the lubrication condition and scales as ΔP = d²u/dr². The boundary conditions are u(0) = 0 (no-slip condition at your lips) and u(H) = U, the velocity at the fluid-spaghetti interface U = 1/2μ ΔP H².

There's still a no-slip condition at the fluid-spaghetti interface, so the spaghetti experiences a shear stress (hydrodynamic drag force) per unit length approximately given as 2πR*μ dU/dz = πΔPRH; the total hydrodynamic drag force is πΔPRHL, where L is the length of the annulus. This must be greater than or equal to the gravitational force acting on the spaghetti (length L') F = πρgR²L', in other words 2ΔPHL/ρ'gRL' > 1 for the spaghetti to be pulled in.

The spaghetti is a passive player; all the action is created by the film of moving fluid.

 

[Chestermiller]

I think this is the wrong approach- the fluid flow around the spaghetti is the essential part, not any solid-body mechanics. The pressure difference generates fluid flow through the annulus; this fluid flow is what generates sufficient shear stress to draw in the noodle (uncooked or not). The problem should first be simplified by 'looking down'- this reduces the problem to an axisymmetric 2-D velocity profile with coordinates (r,z). The z-direction flow velocity in the annulus can be approximated in the lubrication condition and scales as ΔP = d²u/dr². The boundary conditions are u(0) = 0 (no-slip condition at your lips) and u(H) = U, the velocity at the fluid-spaghetti interface U = 1/2μ ΔP H².

There's still a no-slip condition at the fluid-spaghetti interface, so the spaghetti experiences a shear stress (hydrodynamic drag force) per unit length approximately given as 2πR*μ dU/dz = πΔPRH; the total hydrodynamic drag force is πΔPRHL, where L is the length of the annulus. This must be greater than or equal to the gravitational force acting on the spaghetti (length L') F = πρgR²L', in other words 2ΔPHL/ρ'gRL' > 1 for the spaghetti to be pulled in.

The spaghetti is a passive player; all the action is created by the film of moving fluid.

Thanks Andy. To me it is clear that this problem involves a coupling between the solid mechanics and the fluid mechanics. I have carried out the hydrodynamic lubrication modelling that you have suggested in the above post and, for a rigid horizontal rod, have obtained the result I indicated in post #67:
$$V=\frac{rh}{2\eta L}\Delta P$$
Note that, for this case, the "pressure flow" component of the lubrication flow is negligible compared to the "drag flow" component.

I plan on continuing the analyses, first for a vertical rigid rod model and then for an actual flexible noodle model (where the solid mechanical part needs careful consideration). I'm confident that, when you see the details of the analyses, you will be happy with what I have done.

 

[Baluncore]

What is objectionable about carrying out this often repeated experiment in public?
A. The sound.
B. Etiquette.
C. Sauce dispersal.
D. All of the above.

I believe the fluid involved as a lubricant must be the sauce. The lip-seal against the spaghetti allows some sauce to enter with the spaghetti. If too much sauce enters, then a lubrication seal failure will occur allowing air to enter, making the characteristic popping sound, suggesting answer A.

It is necessary for the experimenter to dynamically adjust the lip-seal so as to regulate the lubricant wedge formed from the external lip reservoir. Unless the experimenter has a beard, too good a seal can lead to a poorly balanced nutrition as the sauce drips from the chin, suggesting answer B.

There is also a conservation of momentum and energy consideration. As the tail of the spaghetti travels upwards and then turns to enter the superior orifice, an effect like a whip-crack occurs that disperses excess lubricant sauce vertically, suggesting answer C.

Notes:
I find it interesting that, within reason, the diameter of the spaghetti or noodle is not critical in determining the exercise of this experiment. The limitation is actually determined by the ratio of the height of the lip-seal above the source reservoir : to the pressure difference available across the lip-seal.

I have carried out an experiment that showed I can only blow about 1 psi of static pressure before air is first pushed into the salivary ducts, with the associated risk of air embolism. It would appear that I operate on an internal pressure of about 1 psi. I can however suck a depression of about 14 psi. Given that the density of cooked pasta is close to unity, that limits the length of a pasta “barometer column” to be close to 9 metres. Unfortunately, spaghetti is not locally available in lengths greater than about 500 mm, so I cannot immediately confirm that height by experiment.

I do however notice that “two minute noodles” come in a pack that is often extruded, dried and then packed as a single length. By identifying and tagging the free end it would be possible to rehydrate the noodles without stirring, then to draw a single noodle thread back from the bundle.

But my concern here becomes one of quality control, that of the Chinese noodle product versus the Italian pasta product.

I suspect that the tensile strength of a pasta thread can be enhanced by optimisation of the rehydration process. By adding excess salt to the water, osmotic pressure will significantly reduce the entry of water into the pasta, which will then remain “al dente” and so have a greater structure to water weight ratio, giving a greater tensile strength.

Further experimentation with the “pasta barometer” is clearly needed.