CaptainPanic

That's because you ignored the new word you learned from swansont: Brachistochrone Here's a youtube video of our problem: Youtube has several videos showing the problem... I linked to the shortest of them all.

Things similar in tracks A, B and C: All 3 balls will start with velocity = 0 m/s All 3 balls have equal potential energy All 3 balls will arrive at the end (right side) with equal velocity, and therefore equal kinetic energy. Things different: The acceleration is different: balls A and B will start the same (while ball C doesn't move much at all). At the 2nd slope on track B, ball B will accelerate even more. Ball B will leave ball A behind. When ball B reaches the "up" slope (on the other end), it's well ahead of ball A. the "up" slope might slow ball B down, but only to a velocity equal to ball A. Therefore, ball A cannot catch up. Meanwhile on track C, ball C is still having a siesta.

At the end-point, they will have the same kinetic energy (assuming zero friction). But they will not arrive at the same time. That's easily visualized by this: If your statement were true, then the balls at A, B and C would all arrive at the same time. But I don't think C is going anywhere soon. The acceleration is different for the different tracks.

But the speed is very relevant, because kinetic energy equals: [math]E=0.5\cdot{m\cdot{v^2}}[/math] And hydrogen has a much higher speed than nitrogen, at the same temperature. I explained this once in another thread (post #8). Since we're now confusing the novice people, I fear that I cannot leave out formulas. I have to go straight for the answer. What's the velocity of a molecule? It depends on temperature and molar mass. Nitrogen (N2): [math]\overline{v}=\sqrt{\frac{8\cdot{R\cdot{T}}}{\pi\cdot{M}}}=\sqrt{\frac{8\cdot{8.3145\cdot{298}}}{3.14159\cdot{0.02802}}}=474.5 m/s [/math] Hydrogen (H2): [math]\overline{v}=\sqrt{\frac{8\cdot{R\cdot{T}}}{\pi\cdot{M}}}=\sqrt{\frac{8\cdot{8.3145\cdot{298}}}{3.14159\cdot{0.002016}}}= 1769 m/s [/math] Kinetic energy is equal to: [math]E=0.5\cdot{m\cdot{v^2}}[/math] Nitrogen: [math]E=0.5\cdot{0.02802\cdot{474.5^2}}=3154 J/mol[/math] Hydrogen: [math]E=0.5\cdot{0.002016\cdot{1769^2}}=3154 J/mol[/math] Tadah.

I care about animal happiness, but I realize that without predators, breeding and unlucky deaths, the animals wouldn't have evolved to be what they are today... therefore I continue to eat them. Flies evolved to be what they are because for millions of years, animals and humans have tried to kill them, either because they're food or because they're just annoying. Therefore, one could argue that not killing a fly actually means that you are not behaving naturally. You're preventing a survival of the fittest. I don't kill animals for fun. But a fly will die if it's annoying (meaning it's inside the house). And I kill one type of animal whenever, wherever. Mosquito's. I see no purpose for those pesky insects. I hate them, and I hope they go extinct, and I actively help them to achieve that (the traditional way - no chemical toxins). And anyway, animal happiness is a vague concept. What animal is happier? The pig in the shed who has plenty of food, but a lack of space? Or the zebra on the open plains, dying of drought or a painful and slow death by some predator or disease? We hear a lot about the food industry, but animals in the wild really don't live such happy lives as we imagine. It's just that in children's books, the lion and the zebra are friends, and animals never die. Reality shows that animals get many more than 2 young per couple, and still struggle to maintain the population. (note that for the sake of the discussion, I totally neglected the fact that I disagree with unnecessary animal cruelty)

Is that transmit as in: "absorb and emit" or as in "allow to pass through"? If it is the second one, should be possible to make a lens for IR? With a focal point? Wouldn't that be what was asked in the 1st post? Somehow there seems something wrong with the concept (putting all practical issues aside - looking only at theory: thermodynamics and optics). Because every object emits IR radiation, with an IR-lens it should be possible to always heat something up, regardless of the orientation of the lens or the temperature of the IR emitter.

Umm, yeah. That's what I meant, obviously.

The normal way to focus heat is a "heat pump", which uses the same principles as your fridge. However, a heat pump has absolutely nothing to do with focusing IR. About concentrating IR radiation, some questions: 1. What type of solid does NOT absorb infrared? Because if we want to build some IR lens, it should not absorb IR. But I am no expert in this field. 2. Does IR radiation bend in a lens (if it's not absorbed) just like ordinary light? We need to be able to bend it at least a bit in order to focus it.

1. Which towel absorbs more water? Do we assume they have equal amounts of water (in real, that is not true). 2. How is the reflection influenced by the water? Because evaporation is caused by the towel heating up. How fast it heats up is determined by: (a) the sun, same for both and (b) reflection (not the same). 3. What's the surface area of the nylon towel? Cotton generally has many small fibres, and therefore has a huge surface area (which helps evaporation). Nylon comes in different qualities. 4. To dry nylon, you should just shake it dry. Many synthetic clothes can be worn straight from the centrifuge (no need to dry them). Water does not have any affinity for the fibres at all.

No, it's not flash distillation, because in distillation you separate 2 (or more) components form each other. What you describe is just heating up water really really fast. The name of that I don't know, because it's not used in industry for steam production. Pouring water on something is only used to really quickly cool the "something". In that case it's called "quench cooling". Steam production is done more efficiently. It might be just "flash evaporation", which does not necessarily include a separation. But usually a flash is a reduction in pressure rather than an increase in temperature. My best guess for the name of what you describe is "instantaneous evaporation", or something like that. If you can explain us why the water is poured on the vessel, then we can maybe find the name.

I believe that ray tracing is regarded as a possible future option for rendering. It has some benefits over other methods (for example: reflections and shadows are relatively easy). I only have some minor experience with this. I am not able to say whether any games are actually being developed using ray tracing at this moment.

Did anyone inform you that cars have a second purpose, namely transport of people and other goods? Guns are designed only to kill people and possibly animals, and that makes guns different from almost everything else in the world.

A gas is made up of molecules. So, a mixture of hydrogen gas and nitrogen gas will contain: hydrogen (H2) and nitrogen (N2) molecules. Can you say anything about any possible difference in speed between the hydrogen and nitrogen molecules in the gas? The temperature of both molecules is the same (because they're mixed).

If it goes supernova, that would be quite a show, I guess. I almost would wish that it blows up tomorrow.

I would immediately start making demands to the aliens to get more help, more resources and more knowledge. If they are that motivated to get me to rule the world, then I am in a good position for negotiations. With sufficient knowledge and resources, I'd simply bribe the earth's population into submission. (Stuff like: Petabyte cd's with thousands of movies, free beer and a 3-day weekend)... Ruling the world is ultimately an engineer's job. It's about efficiency, and making sure who does what. With alien warp-speed super-knowledge, that's a piece of cake.

I'm completely against any type of gun ownership, except by police and army. Over here in the Netherlands, the bad guys usually do not have guns, and I therefore disagree with the argument that if you make guns illegal the bad guys are the only ones having them. Punishment of a similar crime is much heavier if the criminal was armed with a gun, and this prevents even the criminal from using them. In addition, guns are quite hard to find (except perhaps if you're part of an organized crime syndicate or something - but the number of people that are such heavy criminals is very limited - and they generally don't walk around killing random civilians, in stead, they kill each other, which is fine by me). My main argument against guns is: Guns have only one purpose, which is to kill people. However, I can understand that Americans don't believe in making guns illegal. Guns are so incredibly widespread in the USA that it might take decades before the number of guns is actually reduced sufficiently to make a difference. And during those decades, the criminals will have very easy access to guns. Situation over here is different: guns are simply hard to find and the majority of criminals don't have one. Therefore, I propose that we split up this discussion into two parts: - Gun laws in a country where guns are widespread - Gun laws in a country where guns have been illegal for a long time And about Iran: Any nutcase who thinks that the Iranian government would listen to an armed and dangerous mob is just stupid. The moment you use violence against the police, you are going to be suppressed even more. Governments and officials will always restore the peace before negotiating... unless you can actually defeat them in battle, which is unlikely.

Maybe you can post an equation that you think might be useful? Or tell us which parameters are involved? Or explain something about kinetic energy in general? What determines the velocity of a molecule? In short: show us that you tried to understand some of it, and we'll gladly help you... I'm sorry, but saying that you read something 6x is not much help, although it's always nice to blow off some steam and complain. I know how frustrating it can be to really make an effort and still fail. It's not uncommon that the book is to blame, because of an unnecessarily complicated explanation.

I sometimes wonder if scientists also go on religious forums and blogs to spam the message of Evolution with all its proof and examples?

Is anyone monitoring the number of visits per day of the individual subforums? I was wondering if there is any change since we have the new look. I can imagine that some forums are visited more frequently now, while others are less popular (because they're harder to find). p.s. I got used to the new look, and I don't mind the change, but I also don't see many benefits. I think it's a bit confusing that places like physics and chemistry have a main "physics" forum, and then 5 subforums - rather than making all subforums under "science" equal. But I got used to it, and I have no problem finding anything at all.

Well, I humbly apologize if you are really insulted. And I also question your reason for being here. You ask a very general question to which I provide not 1, but 3 (three) links. Therefore I do more than you ask... yet you fail to: (1) say thank you, (2) comment any of the links or (3) post new questions now the initial question has been answered. I question the fact that you even investigated this yourself, since your first and second post do not show any previous investigation (you should ask more detailed questions). You only respond to the tone of my previous post... And that leads me to conclude that you come here just to make us do your homework. You're not interested in the topic at all, and you don't seem to intend to have any discussion. With such an attitude, I also wonder why you're having an account here.

It's an awesome website anyway. Great links and movies. I am not really bothered that they want to laugh in the face of the movement that made us leave the safety of our caves and conquer the world.

Juice and a cheese sandwich First breakfast, then coffee. Keeps me alive until lunch. Occasionally, I eat only fruits (lots of it!) for breakfast. On such a day, I don't need any coffee at all.

Yep. Here. I've reported it as spam.

Wait - you want us to read it. We don't download the e-book. We will not read 58 pages... This gives you a choice: 1. You can discuss downloading of e-books (like we do now). 2. You can summarize the e-book in a post, and start a discussion.

Did you try wikipedia? Or google pictures? Because those previous links, and this one too, are what you find by doing a simple Google search. I admit that [hg lamp] was not very useful in google, because the 1st and 2nd hit were useless, and you have to read all the way down to the 3rd link. But that was the wikipedia site I linked to... and it also showed [mercury vapor lamp] as another way of saying [hg lamp]. That enables you to use this new keyword. Using Google isn't really hard...