Wikipedia:Reference desk/Archives/Science/2007 September 2

= September 2 =

Epicycles and Fractals
Hello. Do epicycles on epicycles look similar to fractals? Thanks in advance. --Mayfare 03:07, 2 September 2007 (UTC)
 * Depends on you definition of 'looks like' - a bit maybe - they look like the patterns from a Spirograph more than anything I can thing of..87.102.42.128 08:54, 2 September 2007 (UTC)
 * An epicycle traced around an epicycle is the kind of drawing you get when you consider something like the position of the Apollo command module relative to the sun when Apollo orbited the moon while the moon orbits the earth and the earth orbits the sun. This isn't a fractal...but it shares some of it's attributes.  An epicycle on an epicycle exhibits some 'self similarity'.  The motion of Apollo around the moon is similar to the motion of the moon around the earth - so there is certainly self-similarity.  But fractals have INFINITE self-similarity - so you'd need to trace an astronaut riding a jet-pack in a circle round Apollo and the astronaut's cat being swung around the astronaut's head on a piece of string and a flea on the back of the cat....etc.  So IF you drew epicycles on epicycles on epicycles to an infinite degree - then what you would have would be a true, honest-to-goodness mathematically correct fractal.  But if you stop short of that then you don't have a fractal.  The reason a finite number of epicycles-on-epicycles LOOKS like a fractal is because when we draw fractals we are lazy and we stop drawing them after a finite number of iterations.  So, if you look at our article on the Koch snowflake you'll see that we only drew the snowflake to a 'depth' of seven iterations.  Drawing more iterations than that would have better approximated the true fractal - but the resolution of our computer screens isn't enough to resolve more than about seven iterations - so there isn't a lot of point going deeper.  The same thing would be true for epicycles - there would come a point where a finite number of epicycles would be 'enough' to make it look like some kind of epicyclic fractal. SteveBaker 14:32, 2 September 2007 (UTC)

So moreover, may I say that Spirographs look like fractals only to a certain extent? --Mayfare 16:44, 2 September 2007 (UTC)


 * No! A Spirograph pattern is just one epicycle.  You'd need to drag a little wheel along the line of a spirograph pattern to make a 'second order' epicycle - but you'd need a lot more than just second order - maybe sixth or seventh order might be 'close enough' to look like a fractal.  SteveBaker 20:48, 2 September 2007 (UTC)

General Principles of Relativity Cant be Applied to light, Why ?
If a person is travelling with a velocity v opposite to the light, the relative velocity of light w.r.t the person must be (v+c) according to the Galliliean and Newtonian Principles of Motion Relativity. But Why doesnt it hold good? In special relativity it sas that the speed of light is constant w.r.t all frame of reference.--Oasa 04:18, 2 September 2007 (UTC)


 * Why? Because the universe doesn't work the way Newton expected at high speeds.  Take any two speeds v1 and v2 (relative to you at rest), and general relativity says that the speed of one relative to the other must still be less than or equal to the speed of light.  Specifically, the net speed will be (v1+v2)/(1+v1*v2/c^2)^(1/2)  76.225.157.167 05:00, 2 September 2007 (UTC)
 * It's actually special relativity that says that. Someguy1221 05:06, 2 September 2007 (UTC)

I am Sorry I Didnt get you to the full extent.Oasa 05:23, 2 September 2007 (UTC)


 * Could someone direct me to a specific article which explains how the speed of light is supposed to be constant relative to all frames of reference? From what I understand, the speed of light is different in a void and has been slowed considerably in controlled experiments.


 * This questions seems similar to "What happens if you're in a car going the speed of light and you turn on the headlights?" The Solar System is already traveling at extremely high velocities from certain frames of reference, so I don't quite understand why two objects already traveling at the speed of light in opposite directions shouldn't have their velocities added to one another just because special relativity says it shouldn't. The whole point is that it's all relative. We don't, and may never, have the ability to perform experiments to prove it one way or the other.


 * I've never been fond of the theory of relativity as a whole, but I'm not fond of willful ignorance either. Could someone please tell me where to find where it is proven that "the speed of light is constant w.r.t all frame of reference?" Thanks. --Demonesque 05:37, 2 September 2007 (UTC)

Thank you Demonesque. Thats what I actually what I wanted to know. The proof and why we must not add simply their velocities. Oasa 05:53, 2 September 2007 (UTC)


 * Not a problem, your question made me think, which I enjoy. And I have the supremely annoying habit of questioning established fact. --Demonesque 05:54, 2 September 2007 (UTC)


 * Relativity does not prove that the speed of light is constant. Rather, Einstein assumed that the speed of light measured to the same value no matter how you try to measure it (that's the most accurate way of putting it, constant in all reference frames is not fully explanatory of his assumption).  Then, Einstein took this assumption to various conclusions, consequences of special relativity.  These consequences (especially time dilation) can be experimentally shown to exist, and are accurately predicted by Einstein's theory.  This is taken as proof by physicists that Einstein's underlying assumptions are accurate as well.  As for relativistic velocity addition itself, it is a mathematically necessary consequence of Einstein's assumptions.  A proof is provided in this paper: Mermin, N D, 1984, Relativity without light American Journal of Physics 52.2 119–24, a very good read if you have access to it.  I would spell out the important steps of the derivation, but I don't have access to that journal right now.  Actually, darnit, I also have a book containing the proof, but I seem to have left it far away from myself...Someguy1221 06:14, 2 September 2007 (UTC)


 * That is helpful, thanks. Ironically it is the mentioned time dilation which has always made me question his theories, as the idea of time as a dimension rather than a concept used for sequencing events has never sat well with me. His accurate predictions is what made him pretty much the only living scientific superstar. However, I sadly can't bring myself to accept a lot of his assumptions, which is why I was hoping for a proof, since I'm certainly accepting of a convincing argument; and when it comes to arguments, it doesn't get much better than empirical evidence. --Demonesque 06:32, 2 September 2007 (UTC)


 * Time dilation is "easily" observable (if you have a billion dollar particle accelerator). When atom smashers make new particles, many of them are unstable and decay with a characteristic half-life.  However, the rate of decay is determined by the passage of time in the rest frame of the particle.  From the point of view of an external observer, the time requires to decay gets longer and longer as the speed of the particles increases with exactly the proportion expected if the half-life is increased via the predicted time dilation.  76.225.157.167 06:55, 2 September 2007 (UTC)


 * Yeah, I'm aware of the use of Muons being used to measure time dilation, as well as high speed flights using atomic clocks, however I don't consider that evidence as conclusive proof of time dilation. Both logically and emotionally I cannot accept the possibility of time dilation as I believe it would necessarily enable time travel. However, I don't want to hijack this discussion towards a topic I've already spent a lot of time discussing pointlessly. --Demonesque 06:58, 2 September 2007 (UTC)


 * You've been asking for proof, but it sounds like what you really want is to understand the theory. These are totally separate things. It's pretty clear you don't understand it right now, and this is causing you a lot of confusion. I don't think Wikipedia articles are a good place to learn relativity at the moment, unfortunately. One online tutorial that I like somewhat is Ned Wright's. Let me know if it helps at all. -- BenRG 11:44, 2 September 2007 (UTC)


 * There are all sorts of experiments that show that the speed of light is a constant. The simplest to understand is the one where you measure the speed of light coming from a distant star in January - then again (using the same star) in July.  If the speed of light worked in a 'Newtonian' fashion then we would find that the two results would differ by twice the speed of the earth in it's orbit because in one measurement we'd be moving towards the star and in the other, away from it.  However, when you do that experiment, you get EXACTLY the same answer for the speed of light in both cases - thereby proving that the speed of light in vacuum is a constant no matter what frame of reference you are in.  This is an experimental fact - quite separate from any theory - and it conclusively proves that Newtonian mechanics is wrong.  So - now you have to come up with something else - and the only theory we have that fits all of the experimental evidence is Relativity.  Now as to why the universe follows Einstein and not Newton...well, that's probably unanswerable.  The speed of light is what it is - just as the charge on the electron, the universal gravitational constant and all of those things are constants.   The fact that it imposes a cosmic speed limit and causes all of those inconvenient relativistic effects is also "how nature works" - there isn't always an answer to the 'why?' question for such fundamental things.  Some things just are. SteveBaker 14:20, 2 September 2007 (UTC)


 * It should be noted that Einstein never came up with his assumptions on his own. If that were the case nobody would have sided with him from the beginning. Rather, he took assumptions that others had already proved or seemed reasonable — i.e., that Galilean relativity should apply to all physical activity, and that the speed of light was constant in a vacuum — and showed that if both were true, strange results would fall out — time dilation is a perfectly logical and natural result of those two facts being true, though it took Einstein's elaboration (which is really quite readable) to make that clear to people, and it took experimental consequences for people to realize that it wasn't just a logical trick that Einstein had pulled.
 * So how did 19th century physicists know the speed of light was constant? Well, let us reformulate that in the way that they thought of it: the speed of light does not depend on the velocity of its emitter. That's a little bit different, and a lot easier to grasp, if we are thinking of light as a wave and not as a particle (forget photons for a minute, they came later and are conceptually very tricky). The speed of any wave does not depend on the speed of its emitter — if it did, you would never have the doppler effect. So it was perfectly obvious, and nothing interesting at all, to a 19th-century physicist to think that the speed of light was independent of the speed of its emitter. It becomes trickier today because we think of light in terms of photons and often exclusively think of them as particulate, but we should remember that it does have legitimate wave properties and in fact most of the time acts something like a wave. --24.147.86.187 16:06, 2 September 2007 (UTC)
 * The trouble for a 19th century physicist was that in order for the speed of light to be independent of the speed of the emitter (as for example is the case with sound waves), there has to be a medium through which the sound is travelling (analogous to the air through which sound waves travel) - and the speed of the listener relative to that medium ought to be what matters. Hence the theory of the Luminiferous aether.  The problem being that the experiment where you measure the speed of light from a star six months apart (or better still, the Michelson–Morley experiment) blows away that theory.  Without the aether being present for the speed of the emitter to be measured relative to...the old theories kinda fell apart at the seams.  Hence the need for relativity.  The very name chosen for that theory ('relativity') expresses that the key point made by the theory back then was the lack of an absolute frame of reference (ie no more aether).  Nowadays, most people have no problem believing that part - the tricky part for us is all of the time dilation effects.  I suspect that, had the theory had only just been discovered, we'd call it something quite different. SteveBaker 16:52, 2 September 2007 (UTC)
 * Agreed 100%, except that it is sometimes worth going back to the aether-like explanations to make things like "the speed of light is constant in a vacuum" intuitive. Unfortunately these days we start by talking about photons and laugh off the aether without really acknowledging why it was seen as so important at the time, and why it was so conceptually difficult to get rid of it, and why things like "the speed of light is constant in a vacuum" feel so odd and unintuitive. --24.147.86.187 23:34, 2 September 2007 (UTC)


 * That bit about the speed of light being identical regardless of which direction the Earth is traveling is very intriguing, SteveBaker. That does seem to prove that the speed of light is constant in a vacuum. Does anyone have an idea where I can find more information on that experiment (or any others you might know if, as well)?


 * Additionally, what methods are used to measure the speed of light? I've never thought about that before this. --Demonesque 22:17, 2 September 2007 (UTC)
 * The experiment in question is the famous Michelson-Morley experiment, which measures the difference of the speed of light between two beams sent at right angles from one another, and finds no difference (no matter how you rotate it; if light was going faster along with the direction of the earth, you should find some difference in some direction). As for measuring the speed of light, may I direct you to Speed_of_light? --24.147.86.187 23:34, 2 September 2007 (UTC)

Thank You !!! Oasa 03:26, 3 September 2007 (UTC)


 * A good reference would be Einsteins General and Special Theory of Relitivity. I belive one of you inhibitations to understanding time dialation is the understanding of Space-Time.  Four dementions that inherently we only percieve as three (being space) and time.  After understanding the Theory you will note the higher the velocity of an object through space, the slower it travels trough the fourth demention being time, and vice verca.  Thus the frames of refrence have independent times and thus view velocities accordingly.--Aaron hart 09:33, 3 September 2007 (UTC)


 * Thanks guys! Lots of excellent information here. --Demonesque 23:30, 5 September 2007 (UTC)

How quickly does a fixed point in space move?
How quickly does a fixed point in space move, relative to an outside observer? I have done some research on wiki, but linking the information together is where I need help. For example, according to the Sun article, the solar system is orbiting galactic center at 217 km/sec. The Milky Way itself is moving at 552 km/sec. Even the universe itself is expanding, although whether a fixed point is affected by this, as per Metric expansion of space, is something I'm not sure of, nor do I know what speed to apply to this. In any case, how do these speeds relate to one another? Is our sun, for example, revolving back toward where the Milky Way was, or is it moving along with the galaxy at an effective combined speed of both? And how does the expansion of space affect this?

To put it another way, if I had a particle with no velocity that was not affected by gravity, how long would it take it to traverse the solar system, and how fast - relative to an outside observer on Earth - would one say it was moving? And in what direction (i.e. solar system north to south, across the plane, etc.)? Thanks for your help in advance. Newsboy85 05:45, 2 September 2007 (UTC)


 * The Milky Way is moving relative to what at 552 km/sec? And what is a fixed point? Relativity is sadly very relevant when it comes to discussing things like this. The entire universe is in constant motion, from tiny particles to galaxy clusters. I would guess that the velocity of your fixed point would depend entirely upon what it was moving in relation to and what you defined as a point. --Demonesque 05:52, 2 September 2007 (UTC)


 * Due to the complete absence of any preferred reference frame, "fixed points" only exist relative to locatable objects. However, if you want to know how quickly two particles fixed relative to eachother will move, and affected by only the universe's expansion, this paper suggests they'll move apart at a rate of 500 km/s for every million parsecs between them. Someguy1221 06:01, 2 September 2007 (UTC)

To answer the question about what the Milky Way is moving relative to, as quoted from Milky Way: "Another reference frame is provided by the Cosmic microwave background (CMB). The Milky Way is moving at around 552 km/s[40] with respect to the photons of the CMB. This can be observed by satellites such as COBE and WMAP as a dipole contribution to the CMB, as photons in equilibrium at the CMB frame get blue-shifted in the direction of the motion and red-shifted in the opposite direction." I realize that my question is somewhat moot, but I'm just trying to get a better grasp on the concept. I will have to take a look at that paper, however. In any case, if we take the bothersome expansion of the universe out of the equation, how is the solar system moving in relation to the galaxy? Newsboy85 06:17, 2 September 2007 (UTC)


 * Is the article on the Local_Bubble, which the Sol System is passing through currently, of any use to you? I was reading it a few days ago and thought it might be relevant to your interests. --Demonesque 06:26, 2 September 2007 (UTC)


 * Note that although ~500 km/s seems like a high speed when compared to the scale of the solar system (it is almost 20 times the average orbital speed of the Earth relative to the Sun, for example), it is a tiny speed on cosmic scales. The relative motion of distant galaxies due to the metric expansion of space can be 100 times as fast - on a cosmic scale, the expansion of space itself dominates any local motion relative to nearby galaxies. Gandalf61 11:05, 2 September 2007 (UTC)

Insane crossword question driving me crazy
56 Across: Type of star system: Safely get X-Ray (7,6)

You can find it in the Times, Saturday September 1st 2007. The second word is most likely "galaxy" since it's 6 letters and all the letters are there. This leaves the remaining letters to be SFETYRE, so it's an anagram of those letters if my guess of "galaxy" is right. Anyone? —Preceding unsigned comment added by 86.144.233.185 (talk) 12:25, 2 September 2007 (UTC)
 * It's Seyfert galaxy, which incidentally do emit high levels of X-ray radiation. Laïka  13:50, 2 September 2007 (UTC)
 * Wot, no anagram indicator? Bad show! --Anon, 05:35 UTC, September 3, 2007.

Drink mixing
A common piece of advice to young people seems to be "never mix drinks!". Is there any scientific basis for this, and if so, why are cocktails apparently an exception? Laïka 13:48, 2 September 2007 (UTC)


 * The French always advise against mixing grain with grape - so they'd say it's OK to mix beer with (say) scotch - but not with wine. I'm sceptical too - but see if anyone can come up with anything. SteveBaker 14:02, 2 September 2007 (UTC)


 * Yes, it's an interesting question. I know that I'm always 'bad off of it' if I mix lager and cider (be it in a snakebite or by alternating pints. I don't know why - and TBH, I've never stopped to consider why. I'd quite like to know why now... :) --Kurt Shaped Box 14:09, 2 September 2007 (UTC)


 * Alcohol seems to be one of those topics about which there are many legends, for whatever reasons. In simple terms most drinks are roughly equivalent in terms of alcohol.  When I was in college people were always full of advice like "beer before liquor; never sicker".  I suspect most of this is just old wives tales.  Sometimes a person may have a bad experience in one particular situation, so then they assume they know exactly what caused it, usually erroneously.  That said, the chemistry of fermentation is vastly complex, and how a given drink may affect a particular person is very complicated also, so it's possible there's something to some of these stories.  But in general, I consider them mostly BS.  Friday (talk) 16:10, 2 September 2007 (UTC)


 * I can't personally attest to the veracity of the following, but I have heard from multiple sources (including career chemists) that congeners are the basis for this often-repeated observation. Congeners, the various impurities found in alcoholic beverages, may be one of many factors that lead to hangovers. It is thought by some that these chemicals may compete with each other and alcohol for the various detoxifying enzymes in the body, which in general causes these congeners to remain in the body for longer periods of time (and thus do more damage, if they're into that sort of thing). It stands to reason that as one mixes more congeners in the body, more competition is likely to take place for these detoxifying enzymes. Since certain classes of alcohol are likely to have similar congeners, it stands to reason that mixing alcohol classes (and thus mixing congeners) may result in a worse hangover. Tuckerekcut 16:38, 2 September 2007 (UTC)
 * That sounds fairly hypothetical - I'm calling WP:OR! Any sources for this?  Nimur 17:34, 2 September 2007 (UTC)


 * Note that Friday's "most drinks are roughly equivalent in terms of alcohol" refers to those drinks poured into the official glasses. Of course this excludes pints of beer. And most Belgian beers and such are stronger than pilsener, yet usually poured in bigger glasses. And since wine is stronger still, it should be drunk from really small glasses, which I don't recall having ever seen anyone do. On top of that, different Belgian beers and wines have different alcohol contents, so there should be a separate glasses for each (which there aren't). Considering there are so many exceptions, one can safely say it's a load of bull. :) DirkvdM 18:52, 2 September 2007 (UTC)


 * Definitely this is true; however I was assuming someone who was drinking "advanced" beers is knowledgeable about them and thus knows what to expect. In terms of the beers that people who know nothing about beers tend to drink, it's safer to say they're roughly equivalent.  If you're drinking a 9-10% beer, just count it as two "normal" beers.  Friday (talk) 19:04, 2 September 2007 (UTC)


 * Here in the Netherlands, Belgian beers are drunk quite often by people who are not really 'into that', and quite often they are surprised at how quickly they get drunk (although the hangover is often lighter than one would expect). But the biggest problem here is wine. A typical wine glass is about as big as a beer glass, even though it is at least twice as strong. Champagne (or whatever passes for it) is notorious for getting people totally pissed. DirkvdM 09:24, 3 September 2007 (UTC)


 * Regarding the "beer before liquor, never sicker", the companioin couplet is "liquor before beer, you're in the clear", so while that might be old-wives'-ish, it's not on the same topic as the original question. The issue there is one of ordering, and I've heard it rationalized that one would get into a pattern of drinking during the first few drinks and not notice or be unable to adjust the pace appropriately if the drinks become stronger later in the night. the extreme "beer before liquor" is switching up to drinking straight whiskey on a pace with one's earlier beer-drinking—that's a lot more alcohol a lot faster than you were expecting. DMacks 19:38, 2 September 2007 (UTC)


 * It might also have something to do with dehydration. Alcohol dehydrates you (that's the major cause of hangovers, I gather), and perhaps being drunk impairs your ability to notice that, in which case you're better off if the last thing you drink has a higher ratio of water to alcohol.  This is my theory which belongs to me.  &mdash;Tamfang 20:25, 2 September 2007 (UTC)


 * This question reminds me of Wikipedians editing while being drunk. It is too bad that I forgot the URL. Cheers! --Mayfare 22:55, 2 September 2007 (UTC)
 * My opinion is is not the mixture thats the problem it is the sheer quantity of alcohol involved. Six beers sounds a lot, while a couple of beers, two glasses of red wine, followed by a brandy and a port does not sound like so much. It may be time for an alcohol free week. Graeme Bartlett 00:00, 3 September 2007 (UTC)
 * Indeed. It sounds like there's a false perception of consuming less total alcohol because it's spread around differently.  Nimur 02:49, 3 September 2007 (UTC)
 * I just want to through in my two cents, although at this hour its probably not worth much; but vodka always gave me a hangover, I latter learned that it containes a certain percentage of wood alcohol.  Also the amount of alcohol consumed durring a period of time does not have a linear relation to B.A.C.,  This is due to dillution and, thus absorbtion.  Ex. if one takes four shots of 151 on an empty stomach in one hour,  The B.A.C. Will Spike to a much higher level, and then level off, than if one chugged down the equivalent amount of Alcohol in Budwiser durring the same hour.  To be correct It's more or less logrithmic, except for the intital spike.  To state it again the less dilute the alcohol the more redially absorbed, leading to a higer B.A.C. even theough the same amount of alcohol was consumed in the same amount of time.  After the initial spike, the two graphs level off and fall almost identically.--Aaron hart 11:27, 3 September 2007 (UTC)

Timber shipping Markings
How do I find out all the new Timber shipping markings?

I have a book with them in dated 1975 but can't find any updated version Can anyone help me please

Thank tou Julie Simpson —Preceding unsigned comment added by 86.152.210.170 (talk) 15:00, 2 September 2007 (UTC)


 * Are you talking about Waterline markings to determine the load on a ship? Or, do you mean a standardized marking for the transport of lumber ?  Nimur 17:35, 2 September 2007 (UTC)

Food Science Term
I'm trying to remember a term from food science with no luck. It means "the feeling/texture of food in the mouth" or something along those lines. It's a big component of how people respond to food, other than just pure taste. Does anyone have any idea what it might be or where I could ask an expert? Thank you.


 * That would be Mouth feel. DuncanHill 18:12, 2 September 2007 (UTC)
 * Awesome. Thanks. I forgot to sign before too. --Rajah 02:03, 4 September 2007 (UTC)

Interest in fuels from tree sap or resin
It occured to me that, scince tree sap has sugars and resin is a hydrocarbon, perhaps someone is developing fuels from them. I tried looking but as I know little of chemistry I don't know the proper words to search for. My curiosity has grown to a monsterous mental itch. I would be very thankful for anyone who can point me in the right direction.

JimKenneth 17:56, 2 September 2007 (UTC)


 * Ethanol is made by fermentation of sugars and can be burned in car engines - so yeah - sure, you could make it from tree sap. The problem is the amount of sap you'd need in order to make a dent in gasoline needs.  I doubt you could collect enough to make it worthwhile to make an enormous chemical plant to do the work.  But if you have reason to believe that a VAST quantity of this stuff is available on the cheap - then maybe you're right. SteveBaker 20:43, 2 September 2007 (UTC)


 * And note that some tree sap is valuable for other reasons, like sugar maple sap used to make maple syrup and rubber tree sap used to make natural rubber. StuRat 01:45, 3 September 2007 (UTC)


 * Wood alcohol is a common name for methanol, so I presume that trees are more suited to the production of simple, small hydrocarbon fuels. Alternatively, the wood itself is already used as a fuel, in the form of firewood, charcoal, etc.  Nimur 02:51, 3 September 2007 (UTC)

I think you need to look at biofuels, in general any organic matter can be turned into fuel - the important part is the quantity - and it's unlikely that tree sap itself would provide enough volume - what's more likely is to use the whole tree itself as a resource.87.102.47.218 08:59, 3 September 2007 (UTC)

Staying up late
Why, after staying up to 5 or 6 AM, I can wake up very easily at regular hours in the morning, and only start feeling sleepy late in the afternoon? J I P | Talk 17:58, 2 September 2007 (UTC)
 * The first part of your question seems easy to me: your circadian clock hasn't had time to readjust to your new schedule, so it wakes you up at the usual hour. The second part of your question, though, is a mystery to me.  I don't think I've ever heard an explanation of why or when we experience somnolence in response to sleep deprivation.  --Allen 18:09, 2 September 2007 (UTC)
 * No great mystery there, I think; if your body normally requires seven hours of sleep to get you through your day, it only stands to reason that getting two hours of sleep will leave your batteries short. I find the "crash" is worst if there's a break in the day; things will be fine until your break for lunch or whatever.  The shift in activity seems to give your body the idea that you're intent on catching up on your rest and it shifts gears appropriately. Matt Deres 16:28, 5 September 2007 (UTC)

pressure calculation
If a vortex of air was moving at 160 meters a second and with an energy of around 600 joules, what kind of pressure would it put on an object and how far could it displace an flate surface weighing around 75kgs? Does anyone know the way to work this out? Thanks —Preceding unsigned comment added by 80.6.35.136 (talk) 20:02, 2 September 2007 (UTC)


 * As posed, the question is tricky to impossible to answer. What size and shape is the object? I suppose you could assume all the kinetic energy from the air was transformed into kinetic energy possessed by the object, with 100% efficiency, but that doesn't seem a sensible assumption in most circumstances. If that were the case, you could use Ek = m v2; kinetic energy is equal to mass times velocity squared. That would give you the initial velocity of the object anyway. I suppose you could use work done = force x distance, with the work done being equal to the energy provided by the air, but then you'd need to know the force. Hmm. More information needed I think. Skittle 22:56, 2 September 2007 (UTC)
 * Could you give us the surface area perpendicular to the pressure applied?--Aaron hart 09:53, 3 September 2007 (UTC)