Capillary action and adhesion are things that always gets mentioned at the start of Gen Chem II, with the standard picture, and maybe even Eli brings a narrow tube in to show how water colored with laser dye gets pulled up and accompanied by the standard eye rolling in the audience. The physical reason for this is that the water has a stronger attraction for the surface of the tube than for itself, so it "attaches" and pulls itself.Folks at MIT have the "Cat's Tongue" video. First look at the cat in action
Then look at the simulation
and then go back and look at the first video. Advanced students can peer at the end of the simulation and tell us why the column of water when it falls back to the pan, balls up.
And another video for those of you who want to see how the discoverer figured this out
Horatio has figured out the physics of cat napping (and practices it regularly)
ReplyDeleteit balls up because of the capillary instability.
ReplyDeleteAll this time, Horatio thought it was catillary action.
ReplyDelete"Horatio has figured out the physics of cat napping (and practices it regularly)"
ReplyDeleteUnfortunately, I've never gotten the knack of catnipping ...
I always thought that cats "lapped" by jumping up into yours when you sat down!
ReplyDeletesurface tension.
ReplyDeleteLawyer Mouse
(who just finished his second semester of Gen Chem, as a prerequisite for sitting for the patent bar exam.)
Speaking of "cat's got its tongue", Richard Tol appears to have fallen off the face of the earth in the last number of days, a very un-Tol-like silence on the Internet.
ReplyDeleteThe only reference I can find using Google's blog search is (yet another) Lomborg article, this time in the WSJ (subject can be guessed). Tol, of course, will as ever claim that "Lomborg misquotes me", his usual response to all of these tragic misunderstanding when his work is used by the denialists.
Cat lapping,
ReplyDeleteCat sipping,
Cat napping
Cat nipping
Are so very very
Categorically catillary
The Lawyer wins.
ReplyDeleteThe bit that I was intrigued by was the "fracture" of the fluid column (an approx. hemisphere in contact with a cone) and the position of the "fracture".
ReplyDeleteCymraeg llygoden
Eli, it's not just surface tension, it's geometry too. Therefore
ReplyDeletewhat we're seeing is due to a nonlinear capillary instability.
Driven by?
ReplyDeleteNice lot of quips on cats and capillary - but Eli, although the surface tension forces are stronger to glass than air (and so cause the curved meniscus) they don't pull the liquid up the capillary. That is atmospheric pressure pushing it up - the curved meniscus creates a lower pressure below the meniscus (surface tension effects again). Deceptively fortuitous algebra can 'prove' the pull, but a nice thought experiment shows the flaw. Think of a capillary as the stem of an inverted funnel dipping into the water - surface tension forces would have to hold up a huge mass of water, and they don't!
ReplyDeleteIan