Wikipedia:Reference desk archive/Science/2006 August 9

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[edit] Lithium ion batteries

Why do they have 3 terminals? one positive, one negative.. and the third? pogetive? 00:49, 9 August 2006 (UTC)

I would think the third ground. — [Mac Davis] (talk)
Could be for charging. Not sure--Light current 02:55, 9 August 2006 (UTC)

>> I believe it is because the battery contains more than one cell, not sure but probably two. This has advantages for longer life; such as using two 6 volt batteries instead of two 12V for an R.V. but Im not sure as to why. Also lithium ion batteries last between 300-500 charge and discharges, They store best at 40% charge in a refrigerator. They should not be completly discharged, even a full charge is harder on them, Try to cycle 80% percent charge and run down to 20%, charge back to full or 80%. The worst possible senerio is as in laptops or portable DVD players is to keep them pluged in to an outlet, this keeps the battery fully charged at a high temp. You will get longer life out of them if you take out the battery, while using an A.C. Plug.--Aaron hart 09:24, 9 August 2006 (UTC)

My li-ion batteries only have two. Philc TECI 11:24, 9 August 2006 (UTC)
I would take them back to the store for a refund!--Light current 11:46, 9 August 2006 (UTC)
No, theyr'e meant to, they are made to be the same size and shape as a pair of AAs, and fit into the same terminals. So there is not terminal for any more pins. Philc TECI 11:57, 9 August 2006 (UTC)
So it would seem User:Adam_the_atom is mistaken about there being 3 terminals?--Light current 13:01, 9 August 2006 (UTC)
Is that mentioned in Genesis? I didn't know they had terminals in Adam's day.  :--) JackofOz 13:28, 9 August 2006 (UTC)
Lithium ion cells require precise monitoring during charging to prevent them from over heating and being damages or catching fire. The third terminal is often for a battery charge monitoring (a.k.a. gas gauge) IC inside the pack. This PDF (bq27000.pdf) is the datasheet for one of the ICs manufactured by Texas Instruments if you look at the sample circuit on the second page you'll see they make connections for PACK+, PACK-, and HDQ. HDQ is the communications port in this case.
On other packs (NiMH/NiCd, for example), the third pin might be used to measure the voltage of a single cell for controlling the charge cycle and checking for an overdischarged/damaged pack condition. It could also, theoretically, be connected to a thermistor to measure the pack temperature, which is another method to control the charge cycle in non-lithium chemistries. —Bradley 15:04, 9 August 2006 (UTC)
Excellent response. Isopropyl 18:43, 9 August 2006 (UTC)
Makes sense, did I mention my 2 termianl ones were non-rechargeable (hehe, turned out to be quite improtant) ;-) Philc TECI 21:52, 9 August 2006 (UTC)

My cell phone's battery has four terminals; one for ground, one for the the positive voltage, one for a thermocouple (inside the pack), and one for a one-wire bus. I guess the bus goes to some sort of serial EEPROM inside the pack. A lot of other cellphone batteries I've seen have also 4 terminals; I'm guessing their usage is similar to mine. --cesarb 21:27, 10 August 2006 (UTC)

[edit] Sexual power

how can i measure my sexual power(without having sex)?.

Interesting question. What is sexual power, and how would you measure it if you were having sex? --Allen 03:56, 9 August 2006 (UTC)
i'm guessing a large magnet, a coil of wire... Xcomradex 08:24, 9 August 2006 (UTC)

>> possibly by the heat produced??--Aaron hart 08:47, 9 August 2006 (UTC)


Hey i m serious...i m gettin married in few weeks..n i dont know i m capable enough ..i want to measure...isn,t there any method to measure?

There isn't an objective measure. There's a lot of fake stuff, and people like to pretend they are better than they are. It isn't a competitive sport. My tip: if you love one another, and are honest with each other about what you know, and what you like, you'll work it out and have fun. And practice makes perfect: you have the rest of your lives to practice. Notinasnaid 08:55, 9 August 2006 (UTC)

>> SORRY,, but on the serious side, you need to comunicate and both of you will learn; it will just get better and better, don't worry about the first time, relax it will help, as stated earlier you have the rest of your lives to practace--Aaron hart 09:29, 9 August 2006 (UTC) thanks it means to became relax is the main point to increase your power....is there any excercise like swimming or jogging that help me strenthen my power...i want to make my...rock solid...so is there any excercise????

Doctors say dont smoke, dont drink (too much), eat well & healthily, take some excercise, get plenty of rest, dont worry etc. If you do all that already and still cant get it up, I would pop along to the doctor for a quick check up!--Light current 11:14, 9 August 2006 (UTC)
I don't know what you mean by "sexual power". It isn't like how good in bed you are is a direct factor of how strong you are, and there is no simple exercise that will increase that (though sex is an athletic activity—when done right!—so being in shape can help things). Your primary goal should be enjoying it, and making sure your partner enjoys it. This has more to do with talking to them about what they enjoy, and trying new things, than any sort of "sexual power". Take it slow, try to have fun with it, and always remember to think of your partner, and you won't be able to go too wrong. If you are having trouble with erectile dysfunction, that is unrelated to your "power"—a doctor would be the best person to consult about that, they see cases about that all the time, it is not a big deal. --Fastfission 11:42, 9 August 2006 (UTC)
As a woman, I can say the aphorism is true: it's not size (or "power") that matters, it's how you use it. Your new wife will be happy for you to learn how to use it together. I doubt she cares about your "power," whatever you mean by that. --Ginkgo100 talk · contribs · e@ 18:20, 9 August 2006 (UTC)
Or : it aint what you got, its the way that you use it! Or alternatively: It dont mean a thing if it aint got that swing?? --Light current

The Wikipedia article on Sexology seems rather flacid. Maybe it should be a Science collaboration of the month. --JWSchmidt 01:14, 10 August 2006 (UTC)

If your concern is the satisfaction of your future partner, then being relaxed about it is more important than anything else. The "first time" is rarely very good, because you have to learn to understand each other's desires and to read each other's signals. Create a relaxed and romantic atmosphere, take your time, and be generous with both compliments and caressing and other forms of affectionate touching. --LambiamTalk 01:36, 10 August 2006 (UTC)

>>My only other sugestion is don't drink to much alcohol, high blood pressure pills will effect sexual function, and expecially anti-depresents to a much higher degree than reported, other than that you might want to talk to a doctor and try viagra oc ciallias, it even helps people with no problem at all, and just may be the confidence boster you need.

It will be hard to measure. o_o --Proficient 12:22, 10 August 2006 (UTC)
No you mean: It has to be hard to measure!--Light current 14:59, 10 August 2006 (UTC)

lol --mboverload@ 23:57, 10 August 2006 (UTC)

No you cant get one if Ur laughing!--Light current 14:00, 11 August 2006 (UTC)

[edit] Disaster forecasting

How are hurricanes and tornadoes forecasted now? Can they be predicted by measuring wind speeds near the coasts?

You can see them forming on the weather satellite pics.--Light current 12:59, 9 August 2006 (UTC)

Hurricanes can be generally tracked for days in advance. Problem is that people always cut the track too close and don't account for standard errors (ie. it suddenly takes a turn). With tornadoes, one can only track a severe thunderstorm that *could* produce a tornado. Most of the time, people do not take these warnings seriously (since they happen a lot). --Zeizmic 13:11, 9 August 2006 (UTC)

A large percentage of current day weather forecasting (including hurricanes and severe thunderstorms that can produce tornadoes) relies on numerical weather prediction, which involves using complex computer models to simulate the atmosphere and try to predict how systems will progress. Obviously observations such as the wind speeds you mention are also important, especially the upper air measurements we get from radiosondes and the overall views that weather satellites provide that Light current mentions. So, summarizing, observations and rules of thumb from experience are still important in modern day forecasting, but the way we can simulate the atmosphere using today's supercomputers are very important in forecasts. EWS23 (Leave me a message!) 20:16, 9 August 2006 (UTC)

[edit] camera

What are the functions of diaphragm and aperture in a camera?

There is more to 'focusing' than just focus. Check the main Camera article to start. For more details, F-stop, aperture, exposure (photography) and focal length will help; and if you want some more theory, optics or refraction may also be useful. In short, they control how much light can enter the camera- this means a different image is formed. Nimur 13:46, 9 August 2006 (UTC)
Also, Diaphragm (optics), since you specifically asked about this. Nimur 13:48, 9 August 2006 (UTC)
The diaphragm is to help it breathe. — [Mac Davis] (talk)
It also keeps it from getting pregnant. --Fastfission 16:19, 9 August 2006 (UTC)
Oh dear, oh dear. Can we keep it serious please! 8-)--Light current 17:06, 9 August 2006 (UTC)
Yes, F, stop. (F being Fastfission) :-) StuRat 18:15, 9 August 2006 (UTC)
Nice one. :) Serious follows. DirkvdM 18:52, 9 August 2006 (UTC)
The Dog Star — ['Mac Davis] (talk)
Oh JC! Cant you all focus on the question--Light current 00:41, 10 August 2006 (UTC)
In an attempt to give an actual answer, the diaphragm regulates the aperture (the hole through which the light enters the camera). There is a constant trade-off between the amount of light and the sharpness of the image. The bigger the hole, the more light will fall into the camera, meaning that you can use a shorter exposure time, resulting in less movement blur (movement of either the subject or the photographer's hand). But a bigger hole also means that any point on the subject will be projected on several points on the sensor or film (forming a little circle), also causing an unsharp image. Perfect sharpness would be achieved with an infinitely small hole, but then the exposure would have to last infinitely long, and most people can't stand still that long. DirkvdM 18:47, 9 August 2006 (UTC)

As the aperture becomes very small, diffusion decreases sharpness. A pinhole camera mav an aperture as small as, literally, a pinhole, but putting a pinhole sized aperture in a good camera would greatly lower the sharpness. There is not a "constant tradeoff" with smaller aperture producing greater sharpness. See lens test data for various lenses. It is very definitely untrue the "Perfect sharpness would be achieved with an infinitely small hole.." One such site, http://www.hevanet.com/cperez/results.html says "Theoretic Diffraction Limits Theoretic diffraction limits at f/22 for green light is 68 lines/mm. By comparison a lenses f/32 diffraction limit is 47 lines/mm. If you look at the test results for all the lenses tested at that f-stop they very nearly ALL perform at that limit. See also a discussion of diffraction, circles of confusion and depth of field in books by Ansel Adams.Edison 19:14, 9 August 2006 (UTC)

Of course, I forgot. The laws of nature have a tendency to break down when the variables get extreme values (extreme with respect to the scale we view the world in, that is, because that's the scale we base our laws on). DirkvdM 13:18, 10 August 2006 (UTC)
I hope that eventually we will have nothing but digital pinhole cameras (which will require highly sensitive photon sensors to allow a quick exposure time). This would allow for pics which are completely in focus, not having to choose between having the foreground or background in focus. I see having to set the exposure time, aperture, focal length, and flash as akin to old cars that required setting the choke, then hand cranking the engine. This is all silly archaic crap we can well do without. StuRat 20:29, 10 August 2006 (UTC)
A large part of artistic photography is about setting those parameters to get the effect you want. You can open the aperture and cut the exposure time to draw attention to a specific object, while blurring out the foreground and background. Or you can stop down the aperture and increase the exposure time to generate motion blur -- or even blur moving objects entirely out of the picture. You can underexpose the scene to generate a dark, moody feel, or overexpose it to bring out detail in shadowed areas. An autoexposing fixed-focus camera like a film point-and-shoot is actually quite limited in what it is useful for. --Serie 21:15, 10 August 2006 (UTC)
Yes, but all those things can be done in post-processing on computer, as well, and give the artist more control. For example, it isn't necessary to only have things at one depth which are sharp, with everything blurry at all other depths. You might very well want one object in the foreground to be sharp along with another in the background. For example, a shot with a football in focus, and the player trying to catch it, at another depth, also in focus, with the other players blurry. This method gives you the freedom to change the pic later (assuming you retain the original), should you want to put the focus on the player scratching his crotch. What could possibly be a higher form of art than that ?  :-) StuRat 21:24, 10 August 2006 (UTC)
I was thinking the same, but that might be even more work than adjusting the camera (so one might build both options into the camera). And motion blur would be impossible because you would need more background than you get on the photo. Also, this is indeed more artistrickery than photography. DirkvdM 06:56, 11 August 2006 (UTC)
You can make a version of motion blur that's virtually indistinguishable from the real thing, using a good photo editor. The "missing background" would only be an issue for extreme levels of motion blur. Typically, you only want enough blur to show that there is motion, not so much that you can't even make out the moving object at all. StuRat 07:07, 11 August 2006 (UTC)
Well, I've never tried this. Have you? Edges are hard to get right in my experience. If you zoom in and edit pixel by pixel you might think that one wrong pixel won't matter, but when you zoom out it stands out like a sore thumb. But then that may only be with sharp edges, so maybe you're right. DirkvdM 20:25, 12 August 2006 (UTC)
I would never try doing this a pixel at a time. I would think you would need to draw a frame around the object to blur, then specify a blur direction, and the pixels in the frame would then be blended with nearby pixels, in that direction only. It should work quite well for solid objects. However, lots of individual hairs could be problematic, much as they are when superimposing one image on another. Perhaps at some point in the future cameras will take pics from two angles, and use that info to identify 3D objects. Then, you would only need to select the 3D object to blur and specify the blur direction. StuRat 20:34, 12 August 2006 (UTC)

I made a pinhole camera and used photo paper as the negative. To avoid the loss of sharpness from printing through the paper backing onto the positive print, I scanned the paper negative and tweaked it with Photoshop to reverse it (both in a mirror image sense and light to dark). The result was pretty good: depth of field from an inch away to infinity, and good sharpness.Edison 03:19, 15 August 2006 (UTC)

Cool. How long was the exposure ? Can you post the pic here ? StuRat 09:15, 15 August 2006 (UTC)

[edit] Ships Floating

Hello, Ive searched the Wikipedia database but couldnt find anything. I woudl like to find a detailed article on how/why ships are able to float and not sink in the ocean. A coin will sink but a huge ship made of steel wont, I knwo it has to do with probably bouyancy? but is there a detailed article in Wikipedia explaining this?

Thanks!

Try buoyancy--Light current 14:28, 9 August 2006 (UTC)

Yep - the buoyancy article has the answers. Basically, the trick is that the ship is hollow! It's mostly air. On average, it's less dense than the water, even though its outside is made of metal. If the ship were solid metal, it would sink just like a solid-metal coin. --198.125.178.207 14:47, 9 August 2006 (UTC)
PS: Of course, that's only if the ship is floating in an ocean of water. If it were floating in a sea of mercury, it would stay afloat even if it were solid steel. Because mercury is just that cool. But ignore me - i'm just confusing the matter. --198.125.178.207 14:48, 9 August 2006 (UTC)

If you made a double-hulled ship with a material like Styrofoam between the hulls (to prevent that space from ever flooding), and the volume of Styrofoam was large enough to float the ship, you really could make an unsinkable ship. StuRat 18:11, 9 August 2006 (UTC)

You wouldn't need the hull either, just the styrofoam. There's a guy in Amsterdam who has built his house on a styrofoam platform and the island keeps expanding as he collects more of the stuff.
At the other extreme, there's a houseboat opposite my house that is made of concrete. Any material will work, as long as the average density (including the air inside the boat) is lower than that of water. DirkvdM 18:58, 9 August 2006 (UTC)
If you don't put the Styrofoam inside something fireproof, it can all burn up, and then the ship could sink. StuRat 23:08, 9 August 2006 (UTC)
See also our Concrete ship page. DMacks 19:27, 9 August 2006 (UTC)
If you used styrofoam passengers, they would never drown, either. But they don't pay as well as the human ones. --198.125.178.207 19:35, 9 August 2006 (UTC)
I like Styrofoam people, they always seem so light-hearted. Although, I must admit, many of them are also air-heads. :-) StuRat 23:08, 9 August 2006 (UTC)
Ok since we seem to get this question every while, is it just me, or is it not because the ship weighs less than the water it would displace if submerged and no water could enter the ship. It seems pretty obvious to me, ships float because they are lighter than water (including the air they contain). Am being stupid or are other people? Philc TECI 21:56, 9 August 2006 (UTC)
That is correct. An equivalent way of stating that fact is to say that the boat will float if its average density is less than that of water. --Bmk 22:42, 9 August 2006 (UTC)

Simple: If the ship weighs less than the water it displaces it will float.
The ship will "sink down" until the water it displaces equals the weight of the ship. So if you have a really wide ship it can have a pretty low Draft (nautical) (depth the ship goes underwater) --mboverload@ 11:34, 10 August 2006 (UTC)

Thanks for barging in with that response. :-) StuRat 20:31, 10 August 2006 (UTC)

[edit] raw bacon

Is raw bacon safe to eat?

Depends on what country the pig came from. — [Mac Davis] (talk)
I Wouldnt try it. I think it, like lots of meats, has bacteria on the surface (if not inside)--Light current 17:08, 9 August 2006 (UTC)
Baste it in something like lime or pineapple juice. Of course, some people say that is "cooking" the meat. --Kainaw (talk) 17:23, 9 August 2006 (UTC)
excerpt from meat page

Meat can transmit certain diseases. Undercooked pork sometimes contains the parasites that cause trichinosis or cysticercosis. Chicken is sometimes contaminated with Salmonella enterica disease-causing bacteria. The recent outbreak of bird flu has stimulated global concerns over public health. Cattle tissue occasionally contains the prions that cause variant Creutzfeldt-Jakob Disease.

Is bacon pork or ham? TITQ.--Light current 17:29, 9 August 2006 (UTC)
According to a site I found, trichinosis is very rare in the United States. Cysticercosis is rare, although less so. I wouldn't recomment eating raw bacon, but at least in the United States (and probably other developed countries where the meat is factory-farmed rather than home-farmed), the risks don't appear to be huge. --Ginkgo100 talk · contribs · e@ 18:30, 9 August 2006 (UTC)
Ochg well, tell that to Dr. Finlay--Light current 00:17, 10 August 2006 (UTC)
Yeah, the pork industry in America today is so clean you can eat it raw. That's why I asked what country the pork is from. Anywhere else it is probably dangerous. — [Mac Davis] (talk)
Why would you want to eat the whole pork industry raw? THat would be making a real pig of yourself 8-))--Light current 05:50, 11 August 2006 (UTC)
Ham and bacon are both types of pork. --Ginkgo100 talk · contribs · e@ 18:25, 9 August 2006 (UTC)
Don't forget pastrami! — [Mac Davis] (talk)
Anything can cause diseases. Raw beef can cause Creutzfeldt-Jakob, so shouldn't one eat steak tartare? Raw fish is also a Dutch delicacy. But I have never heard of raw pork, so I suppose there must be a reason for that. DirkvdM 19:03, 9 August 2006 (UTC)
Note that cooked beef can also cause Creutzfeldt-Jakob, AKA bovine spongiform encephalitis, AKA mad cow disease. The protein which causes mad cow isn't alive, so isn't killed by cooking it. Only incineration works. StuRat 23:20, 9 August 2006 (UTC)
So we should all incinerate our meat before eating it? I like my steak well done so that sounds good to me! --Light current 00:01, 10 August 2006 (UTC)
Eating [any] raw meat that isn't pure Grade A or wasn't especially bred to be eaten raw (like in sushi, for example) is like playing Russian Roulette. Eat enough of it, and you are eventually going to get something in your body that you don't want in there. --69.138.61.168 07:20, 10 August 2006 (UTC)
If you're a vegetarian, this will happen a LOT faster than eventually. :--) JackofOz 11:03, 10 August 2006 (UTC)
Possible nitpick: Russian roulette tends to be lethal. Diseases rarely are. DirkvdM 13:23, 10 August 2006 (UTC)
I have ebola, so there...I win!--152.163.100.137 23:47, 10 August 2006 (UTC)
Trichinosis ensues. --Proficient 12:23, 10 August 2006 (UTC)
Tricky noses? DirkvdM 13:23, 10 August 2006 (UTC)
Trichinosis is a pig of a disease to have and can be lethal!--Light current 14:53, 10 August 2006 (UTC)
Is it possible to say that very old religions prohibited certain meats (or fish) and also prohibited eating carrion (leave it to the dogs) just because the rules they wrote down were true, but only before men cooked their food ? Then there would be a hint of that in mosaic law. -- DLL .. T 17:27, 11 August 2006 (UTC)
It is possible to "say" anything. Whether it is correct is another matter.
It is a universal human trait to attempt to find "meaning" behind everything. We seek to find patterns and relationships. On the one hand this leads to tying facts together to discover scientific laws. On the other, it leads to conspiracy theories. (I am not claiming that all hypotheses of either type are necessarily correct or incorrect, just that the drive to find meaning in the universe is the engine that powers both, ... and other things too.)
Digressing for a moment, in discussing evolutionary adaptations and the development of organs, body chemistry, etc, we often fall into the trap of stating that such-and-such is "for" something or other. This is a capital mistake and a fatal error leading to all sorts of incorrect notions. For example, it seems clear that insect wings are "for" flying. On the other hand some wingless insect never gave birth to a fully-winged child. This leads some folk to wonder what good half a wing would be for flying. Gliding perhaps? Well, the mistake is in assuming that wings were initially developed "for" flying. It actually appears that a wingless insect with a tiny proto-wing would have some small advantage in heat regulation. Over time this advantage would lead to larger proto-wings. Only after the wing had developed would it be put to the use of flying. Notice how the assumption that there was a specific meaning in the development of the wing is what lead to the question of flying with half a wing.
That was quite a digression, all right. Note that even the slightest suggestion of a wing would help to extend the length of a jump, and better wings would make jumping progressively better, until gliding, and then flying, was possible. StuRat 21:18, 17 August 2006 (UTC)
To return to the issue at hand, yes, it may well be that early societies noticed that eating certain things might be detrimental, and so banned the practice. Some biblical laws are so obviously sensible that societies that never heard of the bible developed them themseves (eg: the prohibitions on murder, theft, and perjury). However, in the case here, additional other possibilities exist. One might also consider the notion of communal distinctiveness - they do that, we do this. There is also the notion of inculcating self-discipline over a relatively minor matter as training for having it in regard to more weighty affairs. Or it could have been based on a combination of such reasons. Or no reason at all, merely whim. Any of these is possible. And it is immaterial in this context whether one believes that these regulations were divinely promulgated, thought up by Moses himself, or developed naturally over time. The point is that it is impossible to state for a fact the "purpose" behind such regulations, although, of course, one may speculate. B00P 21:52, 11 August 2006 (UTC)

[edit] Flammable

Is vegetable oil or grease flammable?

Yes. Many kitchen fires are caused by oil and grease catching fire on the stove. (Use baking soda & not water to put out the flames!) -- Scientizzle 18:50, 9 August 2006 (UTC)
Or you could put a lid on it (literally, I mean, on the pan - I'm not being rude this time). Water will worsen the fire, ironically. If you mix petrol and water 2:1 (or was that 1:2?) you get a brighter flame than from just petrol. So why isn't water mixed with petrol in combustion engines? DirkvdM 19:08, 9 August 2006 (UTC)
It would rust your block and break your pistons?--Light current 00:24, 10 August 2006 (UTC)
Brighter flame != more energetic. --Jmeden2000 19:14, 9 August 2006 (UTC)
If I remember correctly, brighter flames indicate insufficient oxygen consumption. Clearer flames are hotter. Isopropyl 19:19, 9 August 2006 (UTC)
I'd guess that the water causes the oil to spread out on a surface, thus giving more surface area for combustion, which might result in a brighter flame. There could be other processes at work though --User:bmk
The main reason not to add water to an oil fire is that it causes flaming bits of oil to splatter around the room, which is enough to ruin anyone's day. StuRat 23:14, 9 August 2006 (UTC)
Tested by myself and confirmed. Don't throw water on any petroleum/grease fire. EVER. I am unaware of how well mist works, but I suspect it would never have enough thermal capacity to absorb the heat and stop the reaction. --mboverload@ 11:27, 10 August 2006 (UTC)
A very fine, concentrated mist will work quite well to extinguish nearly any type of fire (a few oddball cases like burning metals excepted), including burning grease or oil. The trick is twofold. A very fine mist is made up of very tiny droplets of water. When these droplets approach a hot fire, they evaporate; this conversion from liquid to gas absorbs a great deal of heat. A side benefit is that this water vapour will not sustain combustion; it displaces oxygen. (Note that generating a sufficiently fine, concentrated mist requires firefighting equipment designed for that purpose; improvised efforts are likely to fail spectacularly.)
Meanwhile, a stream of water – or even large droplets – won't work for the reasons discussed above. The individual droplets are able to stay largely intact when they approach the fire—they just don't boil/evaporate fast enough. You lose both of those beneficial effects (cooling and oxygen displacement.) When they hit the hot oil they heat very rapidly to and above the boiling point. This rapid boiling throws oil everywhere, expanding the fire. Worse, the process breaks the oil up into small droplets with a large surface area that's ideal for encouraging combustion.
See [1], [2] for some discussions of use, or Google water mist fire suppression. TenOfAllTrades(talk) 13:34, 10 August 2006 (UTC)
Oh ok, cool. I wasn't sure if anything less than a stream of water would do it. --mboverload@ 22:12, 10 August 2006 (UTC)
Back to basics : Is vegetable oil or grease flammable? Yes, see Oil lamp. Else, where would you store genies ? -- DLL .. T 17:22, 11 August 2006 (UTC)

[edit] What is dam3?

Hi. I am trying to find a definition of dam3, or dam cubed, in relation to the measurement of volume. The "3" in this case is superscript, indicating cubed. This term is used in the volume measurement of the storage capacity of resevoirs and dams, but it also seems to be used to describe flow. I am trying to find a definition, but Google and Wikipedia don't seem to have anything. I have never heard of this term, but the reports that I am reading use it extensively. Thanks

Cubic decametres. 1 decametre = 10 metres. --Heron 21:27, 9 August 2006 (UTC)

Awright, excellent! I didn't realize it was a standard metric prefix. So 1 dam3 = 1000 cubic meters. My confusion on why it is used in flow measurements is answered by realizing that the reports I am reading add the cubic meters/second up for a month and report the total in dam3 units. So the number of seconds in a month (60X60X24X30) is multiplied by the flow rate, say .970 meters cubed/second and divided by 1000 to give dam3. So, I have to do about 1000 of these calculations for my present report, which is why I am going to go and drink a lot of beer.

Why do that. Why not put the formula into a spreadsheet like Excel and let it do all the calcs? Then you can spend more time drinking! 8-)--Light current 05:13, 11 August 2006 (UTC)

[edit] Molten-carbonate fuel cells (MCFCs)

Could one of these cells be used to power a magnetoplasmadynamic thruster capable of carring up to five hundred tons?68.120.69.0 21:06, 9 August 2006 (UTC)

Until now I was not familiar with MCFCs, so I apologize if this is not accurate. Also, I'm not sure what you mean by "carrying" five hundred tons. Do you mean could it "provide five hundred tons of force"?
If so, I'd say the answer is certainly not yet. Plasma rocket design is a very new science, and there are a lot of possibilities, but it seems that the state of the art (according to NASA here) plasma thrusters are operating at about 1 Megawatt and producing 22.5 pounds of thrust. On the "supply" side, this site from the DoE shows a picture of a 1 megawatt MCFC plants, and it looks pretty big. No matter what the scaling law of power vs. thrust is, to scale 22.5 pounds up to 1 million pounds (500 tons) would result in a mammoth MCFC plant. I don't know what applications you have in mind, but I don't see it happening any time soon. But this is all my quick and dirty research, so feel free to correct me (as always). I'm curious though, why do you ask? MCFC seems like an odd power source for space propulsion. --Bmk 21:52, 9 August 2006 (UTC)

Well I was reading the fuel cell page and there was a table showing that this cell could produce 100MW so I thought that may be effeicent enough power for electric thruster of some kind. A link from the MCFCs page showed one at a fair and it wieghs around 20 tons so I was just curious if it produced 100MW and possibly if it did, could it produce enough lift to lift itself and the thruster along with other things.

Ah, I see. Interesting idea. This might work in space - where the power plant is weightless, and you're only working against inertia (I believe plasma thrusters require a vacuum to operate, anyways). However, I still see it as impractical, even in space, because there is probably a large energy requirement to melt the salt electrolyte to get the plant started. --Bmk 22:50, 9 August 2006 (UTC)

Thank you for the help. Its just another crazy idea.

[edit] Swallows, Magpies, and Trains, oh my o:

If an eastbound Swallow takes off for Capistrano flying at a velocity of 299792457 m/s and starts to exibit relativistic effects shortly after crossing the Rocky Mountains, while at the same time a westbound train takes off from Cleveland, assuming that the westbound train is accelerating at a constant rate of 24 feet per hour per second, from a start velocity of 24 feet per leapyear. Assuming that the swallow is around 8 ounces and carrying a one pound coconut, and assuming that said swallow has exactly the nessesary drag coefficiant in order to maintain the air-speed velocity at a constant value, and mandating that said swallow does not attempt to deviate in a southerly direction while following the sun, and assuming once again that the train is of sufficient size and velocity that it does observe any quantum effects, and also assuming that it has a nice racing stripe painted on the side, exactly how many flavors of Baskin-Robbins low fat frozen yogurt does the snack car on the train have?--172.163.29.21 22:09, 9 August 2006 (UTC)

I just went through Cleveland on a train last night. I do believe the answer to your question is 0: I saw no frozen yogurt on the snack car. digfarenough (talk) 22:41, 9 August 2006 (UTC)
The question is invalid as it contains spelling errors!--Light current 00:35, 10 August 2006 (UTC)
Two even! Separating them was a drag. DirkvdM 13:46, 10 August 2006 (UTC)
An African or European swallow? User:Zoe|(talk) 01:57, 10 August 2006 (UTC)
I find this train of thought relatively hard to swallow. DirkvdM 13:31, 10 August 2006 (UTC)
That said, the answer is of course none, because according to Google there is no such thing as "Baskin-Robbins low fat frozen yogurt". And we all know Google is the measure of all things. Anyway, even if it did exist, wouldn't it melt as a result of the internal friction caused by the stretching at the speed the train would eventually reach? Assuming it doesn't crash into the ocean before then, which is likely considering the low acceleration. In which case the ocean water would enter the container, melting the yogurt anyway, so there you go. And so do I. On to the next bit of exquisite nonsense. DirkvdM 13:40, 10 August 2006 (UTC)
Relativistic length dilation doesn't cause internal friction - but well done on the triple pun in the previous post. And now I'm hungry for frozen yogurt. --Bmk 17:19, 10 August 2006 (UTC)
People should not post their homework questions here. Thanks 8-)--Light current 17:24, 10 August 2006 (UTC)