(no subject)

[jack]

http://www.straightdope.com/classics/a4_184.html

Straight dope asks "How can you suck a strand of spaghetti?" The question being, sucking a liquid, you create a vacuum in your mouth, and it's generally enough to say the pressure within the liquid is less than that in the mouth, so a force acts on the liquid in the straw. Sucking a solid object (eg. pencil), you can say the air pressure cancels out all over, except down the length.

But spaghetti is floppy. The air pressure on the *end* of the strand can't be relevant, because pushing their wouldn't force it into the mouth.

The answer doesn't seem very satisfactory. I'm sure it's something like, air pressure generally acts all over the surface, perpendicular to it, and this cancels out all over[1]. Except on a line through the part of the strand through the lips. So there's a force on that part, propagated down the strand to the next bend (where it acts sideways to the strand).

But I can't really put that into words (or symbols). Can anyone else provide a simple, satisfying description?

[1] May be hard to show, either by common sense or integrals, but we know it *does* because the net air pressure on a strand of spaghetti in midair (neglecting variations with height) is zero everywhere.

Comments

[cartesiandaemon.livejournal.com]

Hm. Two erudite and opposite opinions in as many minutes. I've just tried it with raw spaghetti and contrary to all my expectations it doesn't seem to work Can anyone else confirm this is right?

I expect you're right, and that sounds like it could be, but do you know that for sure, or it just seem the obvious reason to you?

[hairyears.livejournal.com]

No, I just thought about it for a minute, made an effort to recall what it feels like, and stated the obvious.

Googling for the physics of sucking spaghetti reveals no convincing references for my hypothesis.

[cartesiandaemon.livejournal.com]

A brief experiment shows spaghetti only comes in when: it's cooked, I compress my lips, and suck. It's not properly double blind, but two seem insufficient. Of course, I never do suck spaghetti, anyone who has would probably/apparently/maybe know all that already.

That seems to support your theory (though not 100% conclusive).

[cartesiandaemon.livejournal.com]

PS. I emailed the Straight Dope, linking to this thread. It will probably be ten years before they respond, but it would be good to do out bit fighting ignorance.