CaptainPanic

So, now you have to use this formula: [math]Nu=0.13(Gr\times{Pr})^{\frac{1}{3}}[/math] because [math]Gr\times{Pr}>10^8 [/math]... ([math]Gr\times{Pr}=3.08\cdot{10^9} [/math]). Then you know Nu, and you can continue the way I explained. Sorry for not checking the entire answer now... I am not in the mood today for heat & mass transfer - I have my own problems today that I need to solve and they cost enough effort

There are lots of models of the expanding universe, and the model that seems to fit the current observations the best is about an accelerating expanding universe. Please take some time to investigate the topic... I get the idea that you dump a question here to see what comes up. In stead of asking other people to invest time to answer your question, you can also invest some of your own time. Use: -google -wikipedia -the search function of this forum

Everywhere: check the news from both left and right, or conservative and liberal or whatever division you think is relevant for the news topic you want to learn about. Be your own journalist. There is no lack of information, just a poor quality of reporting. We ourselves (and our short attention spans) are to blame. We click, zap and surf and traditional media are using any technique possible to keep our attention until the next commercial break. That means that they will not start an elaborate explanation of all facts, but will prefer to show some screaming people on the street who are being interrupted. The fact that this reporter was pushed around a bit has no news-value, but it IS the only thing that people will remember tomorrow. I believe that many European countries have state sponsored, but supposedly independent tv channels. The Dutch and Belgian versions of that seem more independent than American news, but they too are biased... People are always biased, and news is created by people. [edit] I think that in the Netherlands, traditionally our media have been very biased. Our newspapers are socialist, religious, liberal, etc. The same goes for TV channels (there are many broadcast stations who share the state sponsored channels, and the news agency is one of them). People just knew that this was biased. It was no secret, but in fact the opposite: it was out in the open (the names of the newspapers and channels suggested that they are biased). With the coming of commercial channels, a new type of bias is introduced: the bias to attract viewers regardless of content.

The way I read this is that from an initial sample of 11000, 12000, 16000 or 29000, a subsample of 6000 guns was created for testing. From that sample, 90% was found to originate in the US. I believe that the sample is sufficiently large, so the conclusion can be taken as valid (you can actually calculate the likely error, but I'm not in the mood for that)... But this is assuming that the subsample of 6000 guns was picked unbiased. The fact that no conclusion was reached on the remaining thousands of guns does not mean that they're not from the US, and also does not mean that they are from the US. But assuming unbiased sampling and a sufficiently large sample, we can (with known error) conclude that the same percentage of the untraced guns originates in the US. I don't know enough about guns: Would there be any reason to assume that guns that cannot be traced have a different probability to come from the US than guns that can be traced? Completely unrelated to statistics: if so much drugs can travel into the US, wouldn't it be easy to move some guns out of the US?

Possibly you can help us by defining "thought".

umm... no. You privatize Texas. That means you sell it to shareholders, who will buy this investment. You pay off the national debt with the money thus generated. Apologies to anyone living in Texas - I hope you have some sense of humor. Of course it should be the rest of the world that's privatized, while Texans get all the money.

Put a fence around Texas, and give them their independence. Seems to solve the problem for both sides.

And you want a lamp that gives off roughly equal amounts of light in the entire visible spectrum... And in addition, it has to be one hell of a lamp. The rainbow must be visible, but some thin mist will not even absorb half the light, and it must compete with the Sun! You'll need megawatts in lamps if you want to have a decent size rainbow.

Regarding adding sense to a VR helmet: I think anything other than perhaps water drops (like rain / fog) will be incredibly hard to imitate. I don't think we're so advanced that we can send some signals to a brain and make it think it's in a rollercoaster. I'm not an expert in the field of the human brain, but hooking my brain up to a VR helmet in order to have a 100% real feeling still doesn't seem to do the trick. I mean, what if you want to take a virtual nap? If you put your head on a virtual pillow, you probably still feel the very real helmet. So, not only do you have to give the person feelings, you also have to "remove" some. I thank you for making your signature smaller.

Guys, Let's focus on the science here... We can open a second thread to discuss how much we enjoy drinking, and anti-hangover techniques... But here I was hoping to learn something about the mechanism of how the stomach can influence the composition of the blood stream in a matter of minutes. So far I haven't read an explanation that is explaining it all... (Although a lot of valuable contributions have been made).

The point I was trying to make earlier is that your digestive system is basically like this: Stomach --> intestins --> blood stream Is there any link between Stomach --> blood stream (directly)? If not: how does removing something from your stomach have an almost immediate effect on your blood chemistry? Is the system really that fast (but then why do I need hours to digest food, or to break down other toxins?). I accept that the blood pressure changes, but if I simply run up and down the stairs a couple of times the same will happen, and that doesn't make me feel better at all! There's something missing... still.

I run the risk of hijacking the thread, but you get your national anthem on the radio??? Just like that, without reason? We (Dutch) just hear our national anthem if some sporter won a big race/match... or when there's some special national day. Other than that, never.

Normally, you first determine the Nusselt number, then you determine the heat transfer coefficient using the Nusselt number: [math]Nu=\frac{h\cdot{L}}{\lambda}[/math] But to determine Nu, you have to find out the Grashof (Gr) and Prandtl (Pr) numbers... First of all, your formula's and mine are different. My book says: [math]Nu=0.55(Gr\times{Pr})^{\frac{1}{4}}[/math] for [math]10^4<Gr\times{Pr}<10^8[/math] [math]Nu=0.13(Gr\times{Pr})^{\frac{1}{3}}[/math] for [math]Gr\times{Pr}>10^8[/math] It's funny that the coefficients 0.55 and 0.13 are different. But more important, we now know also that laminar and turbulent can be expressed in terms of Gr x Pr... and this should help you choose between the two. Wikipedia gives 3 formulas for the Grashof number (Gr), and this one seems good for you: [math]\mathrm{Gr_L} = \frac{g \beta (T_s - T_\infty ) L^3}{\nu ^2}[/math], for vertical flat plates. The Prandtl number is also straightforward (and you can sneak into wikipedia to see the formula): [math]\mathrm{Pr} = \frac{\nu}{\alpha} = \frac{\mbox{viscous diffusion rate}}{\mbox{thermal diffusion rate}} = \frac{c_p \mu}{k} [/math] So, now you have the heat transfer coefficient... which you use to calculate the overall heat transfer coefficient (I assume you know how to do that - hint: overall heat transfer coefficient often has symbol U, units [W/m2K], which is the same as the heat transfer coefficient). Also take into account that the air is heating up. Here I am really not so sure, but I'd use the log mean temperature difference as value. I hope that you can take if from there... and I hope that what I wrote is correct. Your problem is a tough one! Good luck with your studies! Heat and mass transfer are a b*tch, but oh so important. And once you've learned it a bit, you're a hero! Unfortunately, it's all empirical, so I had little choice other than post formulas... it's a little bit against the forum rules to help this much (I'm not sure though in this case - please post again if you know the answer from your teacher!).

In addition, I have trouble focusing on anything other than your signature. Is there any particular reason why you think that your signature is the most important thing in your post (because it does get the biggest letters).

I sit in the bus with friends. So we talk. That means I listen to: - Morning show with humorous small talk and pop culture goings-on - News (sometimes "News only"). But I don't listen to the radio - it's all live and personalized. I voted the bottom option, because in the end the question seems irrelevant.

Try to find the eutectic points of mixtures (such as alloys, but not salts with one type of cation and one type of anion). Alloys and mixtures will (always????) have melting points lower than the pure components, if you mix then in the composition that is given by the eutectic point. Check also this one for eutectic copper alloys: http://www.engineeringtoolbox.com/copper-alloys-melting-points-d_1435.html

I would answer the original question with: Because this is a science forum, not a hobby forum. If you wish to make acetylene (burns very hot), KNO3 (for gunpowder), reactive nitrates (for making TNT or some other nitro-compound) or sodium (also to make a nice *boom*, I guess), then I suggest that you go to the nutcase-forum for potential terrorists. If you really wish to learn something and become a scientist, then I suggest that you stay here, and post some decent questions that suggest that you actually wish to acquire some knowledge, in stead of wanting to acquire just a *boom*… Besides, 12 year old kids can also read all our contents, and that cannot be checked. And a 12 year old has no sense of danger yet, but is very interested to show off to his/her friends. They're barely able to distinguish between the terms "metal" and "iron" and shouldn't be trusted yet with a chemical more dangerous than hot water, until they can distinguish between "molecule" and "atom". Finally, there is something called the “war on terror”, and both Europe and America are involved and spend significant amounts of money to spy on everything and everyone. Personally I do not wish to be involved in a forum where one silly special agent could conclude that terrorists get trained. I spend my time and effort on making the world clean, not to break it down... and I don't want anyone to think otherwise. Did that answer the question?

I can come up with an answer, and because your info is limited, and because the problem is quite complex, I don't know it is true or not: If the divers expel air, and it enters the air-pocket, then this should initially push the water level down. This means that the pressure inside that cave is increased (you can say that the water is now pushing up even harder, which results in increased pressure). When a gas is at higher pressure, the driving force to dissolve is higher. This means that the gas from the pocket will dissolve again until it reaches a certain equilibrium value. What I don't understand is why it exists at all. Since the pressure in an underwater cave is most likely higher than atmospheric pressure, I'd expect that over time, the pocket of air disappears completely. The cave is under sea level, but is it possible that the water level in the cave is the same level as the sea surface? That would change the whole answer. p.s. I'm not sure that this belongs in the chemistry forum. It deals with dissolution of gases in water, and pressure - perhaps physics is better?

So, what's the engineering topic of this thread?

BP, I assume is blood pressure, not British Petrol? How does puking alter the blood pressure so fast (apart from the physical effort it takes to puke), because the blood pressure apparently stays at the same level afterwards?

Please include the option "I don't care, I just felt like voting".

Water is everywhere on earth. There is so much of it that I think it's really logical that life needs it. Even if you don't need it, it still comes to you. Even in the driest desert there is some water in the air (as a gas). Since life adapts, and probably started in water, it's only logical that it adapted to make good use of water. Also, water plays a role in many basic chemical reactions such as hydrolysis, photosynthesis and it's also a powerful solvent. And regarding plants and fungi - you can investigate this. My guess is wikipedia. But you can also just look at the metabolism. Plants need light, fungus does not. Plants "eat" CO2 and water. Fungus produces CO2 and water. The fact that a fungus does not run around like a happy puppy is irrelevant. [edit] adding a link to another thread with better answers than my answer here (check Mokele's post).

But you probably know that "please" is a word of 6 letters, not 3 (as in "plz")... We don't mind a mistake, but do not use sms-language. Your post is allowed to be longer than 160 characters.

Although I think it's a bad idea for a lot of reasons (it's complicated, and the sulphur content of food is very low, and the price of sulphur is low - it's a waste product from refineries) But - You could extract it I guess... if you really don't care about the other components, then just combust it, and check literature for a SO2-removal technology. Then convert this SO2 to sulphur. It's a lot of work, and you'll be working with dangerous gases and it requires many steps. It's not worth the effort. What do you need sulphur for anyway?

So what's in my blood that shouldn't be there? Any idea of the type of components? And how can anything pass into the blood from the stomach itself? I thought that intestines were breaking down food into soluble molecules that enter the blood? Throwing up cures the headache very fast (<5 minutes), so I'm guessing that the intestines aren't involved here - they work too slow.