"So, is it ready?"
"Yes sir, all your modifications have been made. The car's just this way."
"That's great! Great. Please... show me."
"Ok sir. First of all, built into the suspension we have an intermittent vibration pulser. These things are tightly controlled, synchronised, and pre-programmed to increase in vigour at your discretion. They'll give a lovely ripple to any standing liquids in the car, either on the dashboard or in cup holders. Hey, you could be holding it steady in your hand and you'll still get the same effect."
<barely containing excitement>
"We've also installed some surround sound speakers into the chassis. These work independently from the car's stereo system. They'll deliver a piercing roar that sounds like it's enveloping the car. It can be quite disorientating, you really don't know where the sound is coming from apart from, maybe, up. (I have some in my Fiesta – for music, but still, they're tasty...)"
"GGggggg! Go on, go on!"
"Well sir, this one we had to work a little harder on. It's certainly not a run-of-the-mill modification. Hopefully it'll be satisfactory. You see the spoiler at the top here?"
"Yeah? Yeah?"
"Well, the mechanism works either from a manual switch control – there's a button down on the driver's side you can press on the sly – or it can be voice activated. Just say..."
"Please. Do you mind?"
"Be my guest..."
"Ok... Ahem... 'Where's the goat?'"
A slab of meat on a spring-loaded arm suddenly flings out of a compartment in the spoiler and lands heavily in a blood-soaked splatter onto the sun roof.
"YES!"-- theleopard, Apr 19 2012 Square wave image. http://3.bp.blogspo...U/s1600/charles.jpg [AusCan531, Apr 22 2012] I think I'll opt for the tree-rapelling package.-- RayfordSteele, Apr 19 2012 Or a cup of water dashboard accessory that indicates you have just been in an auto collison by rippling.-- rcarty, Apr 19 2012 this should be a fiat panda.-- po, Apr 19 2012 The Jack-in-the-glovebox Chucky doll is a bit much.-- 2 fries shy of a happy meal, Apr 19 2012 //Unless its faux meat its going to take a lot of maintenance//
Maintenance? You'd only have to prime it on the day you intend to go camping with the family. But certainly, faux meat could be employed. Which facilitates flexibility in your scare-mongering.-- theleopard, Apr 20 2012 God help us! We're in the hands of engineers. ~ Dr. Ian Malcolm.-- 4whom, Apr 20 2012 //They'll give a lovely ripple to any standing liquids in the car, either on the dashboard or in cup holders. //I think I read the effect was done with a bass guitar string strung under the dash-- AbsintheWithoutLeave, Apr 20 2012 Where's'the hitchhiker?-- rcarty, Apr 21 2012 <whispers>the call is coming from inside your car...-- 2 fries shy of a happy meal, Apr 21 2012 // I think I read the effect was done with a bass guitar string strung under the dash //
I recall hearing that as well. Why they didn't just use a real Tyrannosaurus is beyond me.-- Alterother, Apr 21 2012 A real tyrannosaur would cost too much to feed. A guitar string is only a couple dollars.-- rcarty, Apr 21 2012 Yes, but I've always felt that part of the movie suffered for accuracy. Anyway, they already had the goat.-- Alterother, Apr 21 2012 Anyway, I'd wager that it was an electric bass string, not a bass guitar string.-- spidermother, Apr 21 2012 Electric upright, then? Not a significant difference. Or did you mean electric as opposed to acoustic?
Wait--why does it matter? And why am I asking myself these questions?
Am I the only one in here?-- Alterother, Apr 21 2012 Question: to what extent do the ripples in the cup correspond to the waveform of the exciting vibration?
If you played a loud enough square-wave at a manageable frequency, could you generate square water waves?-- MaxwellBuchanan, Apr 21 2012 [Alterother] No, electric bass. The thing the bass player in a rock/pop/whatever band plays, tuned EADG. It's an electrified descendant of the double bass, and not a member of the guitar family. Even though it's mostly played horizontally, with a strap, it is an electric bass. A bass guitar is something else.
I find these distinctions at least interesting, if not important.
[MaxwellBuchanan] I think you'd get discontinuities rather than square water waves.-- spidermother, Apr 21 2012 [spidey], my wife plays all of them, plus cello, flute, and oboe. There are several prime examples of such instruments in our library (except for the double bass). That's why I was being so oddly specific.
Well, that, and I'm half out of my head on pain meds and bored silly.-- Alterother, Apr 21 2012 //discontinuities rather than square water waves//
Discontinuities as in up/across/down? That would suffice.-- MaxwellBuchanan, Apr 21 2012 Discontinuities as in separate bits of water. A square wave in water would imply infinite acceleration, which in turn might generate singularities and doom us all. Try it!-- spidermother, Apr 21 2012 Actually singularities are OK. Space just sort of gives up and fudges an answer, and it all goes OK.
But, to the square waves. You can create a standing sine-wave in water. Can one not create two superimposed sets of standing waves, one a harmonic of the other, and in the right phase to get a squaroidal wave? Three sets? Four?
I can see that, at some degree of steepness, things will tend towards exotreopy and you'll wind up with a mess. But at what degree?-- MaxwellBuchanan, Apr 21 2012 //Three sets? Four?// Try a million! No, much more!
You can get an arbitrarily close approximation by superimposing harmonics, but a mathematically precise square wave is the superimposition of an infinite number of harmonics.
If you're after a wave that looks fairly squarish, and propagates while maintaining that shape, I think you'll find that that's also impossible - the wave will break, instead. I don't have a rigorous proof of that, though.-- spidermother, Apr 21 2012 //Try a million! No, much more! //
Yes yes. But I was considering only how many sets of standing waves could be superimposed in water. I had assumed that exeotropy would set a limit, but on reflection I think I probably meant nöeoplasy.
Of course you could do it all at scales below the Laplace-Gerridae limit, but that wouldn't be very exciting. (Although, on the plus side, you'd create a water surface which had a fine enough texture to iridesce nicely.)-- MaxwellBuchanan, Apr 21 2012 5 should work fine: 0,3,5,7,9, for the "Bart Simpson" square wave.-- FlyingToaster, Apr 22 2012 //Yes yes.// Yes yes yes, but the rhyme was irresistible.
Gravity waves on water are pretty non-linear. At shorter wavelengths surface tension starts to dominate, depth and amplitude interact, and at all wavelengths the phase speed does not equal the group speed. I think that that all adds up to water-air standing waves being not even remotely harmonic, so the answer to your question might be 1.-- spidermother, Apr 22 2012 [FT] sp. 1, 3, 5, 7, 9.-- spidermother, Apr 22 2012 It's easy to get square waves in water. Use a saw and temps below freezing.-- lurch, Apr 22 2012 //on a sillyscope// realistically there's no such thing as a square wave: there's always slew time.-- FlyingToaster, Apr 22 2012 Linked image of a square wave. Oh, and a bun for [theleopard].-- AusCan531, Apr 22 2012 //there's always slew time.// That sounds very much like the Friday lunchtime beer-meeting. Quality slew time. Yay.-- MaxwellBuchanan, Apr 22 2012 Can I have a free pen please?-- skinflaps, Apr 22 2012 Well, you can have the one we used to keep the velociraptors in.-- Alterother, Apr 22 2012 random, halfbakery