Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.
(Asking this because the previous question was only partially answered) About how much force is required to knock someone out? And how does this compare to the amount of force required to perform a power break on an unpegged stack of 4 standard 1-inch-thick seasoned pine boards? 2601:646:8E01:7E0B:992F:DDCF:CD34:2A70 (talk) 07:09, 12 September 2017 (UTC)[reply]
I see you haven't received a response to this so far. I suspect the question as posed isn't answerable because (a) human beings are extremely variable – an identical blow might be a mere annoyance to one person and fatal to another – and (b) tiny variations in how hard, where, at what angle etc., might make large differences to the outcome on the same person, as might that person's exact state of well being at the time. Crime fiction stories sometimes used to feature strong-arm men who could calibrate their blows with, e.g., a blackjack or cosh so precisely as to render the victim unconscious for a pre-specified number of hours: this was, of course pure fantasy. {The poster formerly known as 87.81.230.195} 90.200.137.12 (talk) 08:29, 13 September 2017 (UTC)[reply]
OK, let me add more details: assume that the person in question has a good chin, is in perfect health, and is pumped full of adrenaline (i.e. extremely pissed off, as is usually the case in an actual street fight), and that the blow is a well-placed (but not necessarily perfect) karate strike to one of his weak points (neck, chin, side of head, bridge or tip of nose, solar plexus, floating ribs, or crotch), delivered with a force which is just sufficient to break the stack of 4 boards described previously. (On second thought, let's make this even harder and assume that the person is not only pissed off, but is also high on crack and meth at the same time.) Is this likely to knock the person out, or at least disable him? 2601:646:8E01:7E0B:3DB7:8D6E:A762:14CC (talk) 11:22, 13 September 2017 (UTC)[reply]
Any blow to the head, neck, or even any other part of the body is potentially lethal. There is no safe impact range for a blow intended to "knock the person out, or at least disable him". Akld guy (talk) 23:47, 13 September 2017 (UTC)[reply]
I don't care whether or not I kill my attacker -- what I want to know is, can he still keep fighting after taking a blow like that! 2601:646:8E01:7E0B:3DB7:8D6E:A762:14CC (talk) 06:31, 14 September 2017 (UTC)[reply]
So, does anyone know the answer to the question: Can an attacker such as that described above (healthy, with a good chin, pissed off, and high on both crack and meth) continue fighting after receiving a blow described above (a well-placed but not necessarily perfect karate strike to one of his weak points described above, with a force just sufficient to break a stack of 4 boards described above)?73.202.74.122 (talk) 20:04, 14 September 2017 (UTC)[reply]
Uh, forget the part about knocking the attacker out -- I've looked up the range of forces for that already, so just tell me, how much force does it take to break 4 boards as described? 2601:646:8E01:7E0B:3DB7:8D6E:A762:14CC (talk) 08:54, 15 September 2017 (UTC)[reply]
When I left for work the humidity in my house was 32%. The house was closed up the entire time and no one was there. When I got home humidity was up to 58%. Why did it go up so much with the windows closed and no one inside? CTF83! 07:12, 12 September 2017 (UTC)[reply]
To explain, the percentages are relative humidity, which varies with temperature. Although with that said, no building is airtight unless it's designed to be; see air changes per hour. --47.138.161.183 (talk) 07:20, 12 September 2017 (UTC)[reply]
It might have, I didn't look at the temp. CTF83! 15:48, 12 September 2017 (UTC)[reply]
Ok , thanks, I'll read that. CTF83! 15:49, 12 September 2017 (UTC)[reply]
Did you take a shower before you went to work? The steam from the shower, and wet surfaces in the bathroom, might have equilibrated out to the measuring instrument's location later.
Another possibility is that the house isn't closed up as much as you think (is there any ventilation or air conditioning etc.?) and the outside humidity went up, or hot air from the outside was brought in and repeatedly cooled off by A/C with moisture accumulating inside etc.
Even something like leaving the lid off a toilet tank has some effect on humidity (or at least, I've done that deliberately in winter believing it alleviated some of the worst of the dryness). Wnt (talk) 23:42, 12 September 2017 (UTC)[reply]
5) A poorly insulated house may have moisture condense out on the walls and windows at night, then evaporate as they warm up during the day.
6) Dripping faucets.
7) Wet dishes.
Also, the humidity may have stayed the same, on average, in your house, with it just evening out while you were gone. For example, if the bathroom or kitchen was humid when you left, that humidity would have spread to the rest of the house, making the reading higher outside those areas. StuRat (talk) 05:01, 13 September 2017 (UTC)[reply]
Thank you all for the help! CTF83! 04:55, 16 September 2017 (UTC)[reply]
You're quite welcome. StuRat (talk) 15:10, 16 September 2017 (UTC)[reply]
Hello,
This is a small tree found in Kerala, a sub-tropical region in South India. It is about five meters tall and has rather catching foliage which causes it to stand apart from the rest of the trees in the neighbourhood. The fruit looks like an unripe guava but much smaller than a guava fruit. Yellowed ripe fruits were seen on the ground but instead of rotten fruits dried, hard, wood coloured ones were scattered under the tree.
https://ibb.co/fDZTtahttps://ibb.co/bZ3hKFhttps://ibb.co/moOtRvhttps://ibb.co/fGupzFhttps://ibb.co/j4uNKF
Can somebody help find out its name and classification? — Preceding unsigned comment added by 117.253.184.183 (talk) 07:23, 12 September 2017 (UTC)[reply]
I'm having some trouble finding leaves or other parts of the tree in focus. Ideally it would be nice to convert the structure of leaves and other parts of the plant to botanical terms. For example, our article on leaf venation gives me the impression that these leaves might be actinodromous, though looking at a better resource like [1] makes me wonder if that is so. But ... with a leaf in hand, and ideally a magnifying glass, you can say so much more than we can say from these photos. Once you have some botanical terms, you might be able to web search relevant trees. Another possibility is to take your guava guess and go through Myrtaceae (the guava family) in search of likely candidates -- though that is a lot to go through with no guarantee of success. Wnt (talk) 23:55, 12 September 2017 (UTC)[reply]
Just a guess, but maybe some type of nutmeg such as Myristica fragrans which our article says is grown in Karela. It fits with the "hard, wood coloured" fruit anyway. Alansplodge (talk) 17:33, 14 September 2017 (UTC)[reply]
Re [2]. This morning at the bus stop I saw a woman with a device roughly the size of a cigar, looking rather like one of those cylindrical cigarette lighters. It wasn't just a cigarette in a holder (there was no glow or wisps of smoke coming from it) and it wasn't an e - cigarette. She held it to her lips and sucked on it and exhaled smoke after. Has anyone seen this before? Can it legally be used indoors? 81.139.183.197 (talk) 09:48, 12 September 2017 (UTC)[reply]
Which country was this in? I'm in the UK, we can't move for the things. Every high street now has one or more shops selling them. Some are the size of bagpipes. There are plenty that are cigar sized, so that the liquid tank and the battery can be large enough to last longer. Usually there's a smaller mouthpiece at one end, resembling an old cigarette holder. The early sort of skeumorphic cigarettes have fallen from favour, at least amongst those with serious habits.
No, you generally can't use them indoors any more. They're still legally vague, but most premises have now made their non-smoking signs specific to prohibit them. Andy Dingley (talk) 10:06, 12 September 2017 (UTC)[reply]
Not yet, although they're appearing for private cars, on the back of child safety justifications. In 2007 we imposed a massive indoor smoking ban on almost all premises (shops, pubs, restaurants, office) almost overnight, and with little opposition. As a result, the population of some towns went outdoors for the first time in years. Andy Dingley (talk) 10:15, 12 September 2017 (UTC)[reply]
And even outdoors, the property owner may impose a ban (e.g. railway stations, hospital grounds). Prisons and mental hospitals were exempt, but that has changed. However, mental hospital wards used to have open verandas on which smoking was allowed on a one - hour - on one - hour - off basis, which may still be the case. Of course, anyone who is not on a section is free to leave the ward and indeed the hospital at any time. 81.139.183.197 (talk) 10:27, 12 September 2017 (UTC)[reply]
Many e-cigarettes are not shaped like cigarettes, and some have similar shape and size to a cigar. What you saw was most likely a vaporizer, and no matter what the size or shape, still generally falls under the name of "electronic cigarette". SemanticMantis (talk) 14:56, 12 September 2017 (UTC)[reply]
It was almost certainly a vaporizer or an e-cigarette. If it wasn't an e-cig it may have been a "vape pen" or a vaporizer which are generally used for cannabis or cannabis extracts. Compare to the "Pax" brand vaporizer for consuming cannabis or cannabis extracts. Other vaporizers are designed specifically to vaporize cannabis extracts variously known as BHO, oil, and many other names. 204.28.125.102 (talk) 22:48, 14 September 2017 (UTC)[reply]
Does a bike on a carrier on the back of a car exert the same pressure or "weight" if the carrier is extended farther outward behind the car? — Preceding unsigned comment added by Missouriensis (talk • contribs) 14:53, 12 September 2017 (UTC)[reply]
I am not sure what your question is, because the choice of words is crucial where you put pressure or "weight". If you are asking about whether it will change fuel consumption, the question is mostly about the drag coefficient of car+carrier with bike vs. car+extended carrier with bike (solid friction between the wheels and the road should be the same, assuming for simplicity that the trajectory of the carrier is the same in both cases - which will be wrong in mountain roads with a lot of turns etc. but I guess the question is mostly for highway).
I guess drag (hence fuel consumption) would be higher for the extended carrier. Essentially, with a very very long extension, you are sure to create two Karman vortex streets, while with a short extension you can avoid the second one. The reasoning is basically the same as the standard explanation of the V-shape for some bird flocks. But the specifics depend on the geometry, of the car speed, etc. TigraanClick here to contact me 15:29, 12 September 2017 (UTC)[reply]
if you are referring to weight of the car on the ground, the total weight is unchanged if the two carriers weigh the same. The weight on the rear tires increases slightly and the weight on the front tires decreases slightly. Theoretically, this will also very slightly tilt the car up at the front, which could result in more lift at speed, which will reduce the total weight on the tires and increase the drag, but I cannot believe this effect is large enough to notice. -Arch dude (talk) 16:47, 12 September 2017 (UTC)[reply]
If the weight of the bikes is extended some distance behind the car then the effect would be noticeable on the suspension on an uneven road, but most bikes are light compared with the weight of the car, so I agree that the tilt on a smooth road would probably not be noticed. Dbfirs 19:47, 12 September 2017 (UTC)[reply]
The weight of the bike rack will exert a torque, which will work to lift the front wheels (of course, it won't be enough to do so alone). StuRat (talk) 01:16, 13 September 2017 (UTC)[reply]
By "extending the carrier farther outward behind the car", you appear to mean a carrier that is designed to be extended. I think you do not mean constructing an extension and bolting it to the existing carrier. Therefore, taking the first meaning, extending the carrier and moving the bike further out on it does not add any extra weight that the car has to carry. What it does do is increase the pivoting about the rear wheels that already existed. The carrier and the body of the car form a kind of lever that pivots around the rear wheels which act as a fulcrum. Moving the carrier and bike further out rotates the whole setup just a little more and transfers more of the weight off the front wheels onto the rear wheels. Therefore, the air pressure in the front wheels is relieved a little and that in the rear wheels is increased by the same amount. The same happens to the pressures that the wheels exert on the road. Neither the total mass of the car+carrier+bike nor their weight change. In a severe case, the weight on the rear of the car may be enough to lift the front wheels completely off the ground. I have seen this happen on a motorway when a light truck towing a trailer ahead of me travelled over an uneven surface at 100 kilometres per hour (62 mph). The trailer bounced the front wheels of the truck off the road, the driver lost control and both vehicles rolled over. Akld guy (talk) 07:22, 13 September 2017 (UTC)[reply]
If that is true then why does a few bags of cement in the tray of a light truck reduce oversteer?Greglocock (talk) 07:53, 15 September 2017 (UTC)[reply]
If the bags are behind the rear wheels, oversteer will be (slightly) increased. If the bags are near the cab, oversteer will be reduced. The trailer, if incorrectly balanced, adds weight to the hitch, well behind the rear wheels. -Arch dude (talk) 15:21, 15 September 2017 (UTC)[reply]
How does US 's level at STEM compare with other countries? — Preceding unsigned comment added by 31.4.145.57 (talk) 18:09, 12 September 2017 (UTC)[reply]
I imagine students do better on molecular genetics questions. ;) Wnt (talk) 23:37, 12 September 2017 (UTC)[reply]
Very likely, both Americans and others. But how was America doing in mathematics, for example, in 1960 compared with the rest of the world; vs. now. ←Baseball BugsWhat's up, Doc?carrots→ 02:23, 13 September 2017 (UTC)[reply]
I'm not sure that we have such data. While standardized tests have been used for a long, long time (in China some several thousand years), in the U.S., it wasn't until the 1980s that broad spectrum universal standardized testing came into being; earlier standardized tests were limited to specific applications (civil service tests, college admissions tests, etc.) the results of which would be hard to apply across all of a population because the test takers were not a random sampling. So, the data you seek likely does not exist for the U.S., and international broad-spectrum testing (where a random sampling of people from all over the world take the same test to compare results) certainly didn't exist. Honestly, the modern travesty that is the standardized testing industry, and the detrimental effect it has had on American educational quality dates only to A Nation at Risk, a report issued in 1983 whose results are based on sketchy presumptions and bad data, and which has been widely criticized since its release, despite (and also because of) its influence. --Jayron32 11:18, 13 September 2017 (UTC)[reply]
I find it interesting that the Ancient Romans were better at war than science and got to rule Greece a few centuries but soon got their asses handed to them while the Greek empire endured 330AD-1453. And that the Greeks only fell when an empire good at STEM got through the capital's wall with a cannon so strong the carriage broke every shot. And that that empire too was nibbled away to almost nothing when Ottoman STEM fell behind. Sagittarian Milky Way (talk) 02:41, 13 September 2017 (UTC)[reply]
For the record, the Romans were great at engineering and applied science (though not so great on fundamental research), and also the Byzantine Empire was a continuation of the Roman Empire and not the Greek one. 2601:646:8E01:7E0B:3DB7:8D6E:A762:14CC (talk) 12:14, 13 September 2017 (UTC)[reply]
Well, it's a bit more complicated than that. Politically, there is no distinction between the Roman Empire and the Byzantine Empire. Culturally, however, the eastern half of the Empire was distinctly Greek and the western half was Latin. The question one should ask is which is more important, the political structure or the cultural one. --Jayron32 13:43, 13 September 2017 (UTC)[reply]
I'd note that comparing test scores over time is always tricky anyway, since requirements etc change, unless you really use the same questions in 1950 as in 2018 which is problematic especially in science. If you consider the British system and those inspired by it (e.g. Malaysian, Singaporean), while there is often talk etc of how students did better this year than last, or lots of worries when there's the opposite, when you have even just a little bit of knowledge of how marking, question setting etc is done, as well as issues like Grade inflation, it's easy to see that it's not really clear whether these changes are meaningful and really reflect changes in achievement, knowledge etc.
That's even before you consider that even the nature of the tests themselves tend to change, as well as issues, particularly prominent in places like Malaysia and Singapore of how much the tests scores reflect the person's ability to use and apply knowledge, and how much of it reflects rote memorisation and learning how to take a test; and how useful the later is presuming you aren't intending the student to spend all their lives taking tests, i.e. even if the people are really achieving more than students 10 years ago, how useful are these achievements?
(There is an interesting issue here though, which also gets at Df's point. While places like Korea, Singapore or China don't seem to show great levels of STEM achievement at university level (albeit they do seem to be improving) compared to a place like the US or even the UK and this is often considered a sign that their systems aren't working as well as they should, it does seem that increasingly a big percentage of university students including at graduate level who do well are people who had a lot of their education in such places. This doesn't of course mean that their school systems are the reason for this. Or even if it is, that it's worth other possible costs. Or even if it is, that it's easy to replicae. Notably the fact that people of similar cultural background who gained most or all of their education in the US (or wheever) tend to likewise perform better on average would be a word of caution against any simplistic analysis.) P.S. Since I mentioned China and also PISA below, I should say I'm aware that China in PISA still does not come close to represeningt the whole of China.
But there are other assessments besides TIMSS though. Notably Programme for International Student Assessment. In 2015, the US was 40th in mathematics and 25th in science. 25 is not too bad, but it's maybe not great for a highly developed country with a very high GDP per capita. Nil Einne (talk) 07:44, 13 September 2017 (UTC)[reply]
The U.S. comes out rather shitty on its Gini coefficient however, which is probably a better correlation to educational access than is GDP per capita. --Jayron32 11:20, 13 September 2017 (UTC)[reply]
However the question then becomes how do you consider the comment "probably not as good as it should be". I would argue that saying that given where we are in the world now as illustrated by our level of development and GDP per capita, we are not actually doing as good as we should be is not American exceptionalism (as your comments taken together would seem to suggest, even though I don't think you intended to) but a fair comment by an American. In other words, my main point with the GDP per capita etc was that based on PISA results at least, I disagree with your criticism of BB's comment, since the based on PISA and what we know about the US, they are not doing as good as theys should be.
While Gini coefficient is relevant, it doesn't IMO support your suggestion that BB's comment requires American exceptionalism. The Gini coefficient may make it less surprising but it doesn't make it significantly more acceptable. Fixing the STEM achivement problem isn't likely to solve the poor Gini coefficient by itself (which is wider sign the US are not doing as good as they should be in the world), but it is probably one factor especially since it's likely to be difficult to solve it without fixing wider problems in educational access.
To be fair, since there is no magic, you might argue that things are where they should be if they are headed in the right direction at the right pace since realisticly there's no quick solution to historical problems but whether with PISA or Gini coefficient, it's difficult to argue this is the case for the US. TIMSS results complicates things somewhat but I don't think we can ignore other assessements.
I appreciate that not everyone agrees that inequality is a major problem that needs to be solved, so I'm not suggesting everyone may agree with this view, but this is a different issue from whether it's American exceptionalism to suggest the US is not doing as good as they should be because self measures show they should be able to do better. (I.E. These people are saying they do not think these measures suggest the US has major problems because they disagree they matter much or at all; they aren't saying relatively the US is doing okay since there's no reason to think we should be able be doing better.) Likewise, some or many of the political solutions to the problems in the US may actually have made things worse because they concentrated on the wrong issues, but this doesn't mean the US is doing as good as they should be except on a level of "well our political systems is screwed up so it's not surprising".
Most of the answers above have to do with the average level of achievement. If instead one chooses to compare the best of US STEM accomplishments to the best of other countries, then the US often comes out looking somewhat better than if you only consider the average. Achievement, so to speak, is not evenly distributed through the US society. For example, the US is at the top or near the top in things like the number of Nobel prizes, the rankings of universities in STEM fields, International Mathematics or Science Olympiad medals, number of academic papers published per year, value of STEM related businesses, etc. Admittedly, some of that is because the US is a rich country that can import top talent from other countries; however, I do think the US has historically had a culture that favored scientific investment and high-level achievement. That hasn't always trickled down to STEM awareness and achievement in lower education though, where large disparities still exist related to geography and income, etc. Dragons flight (talk) 12:51, 13 September 2017 (UTC)[reply]
See my note about the Gini coefficient for why this dichotomy exists. The difference between the best academic performance in the U.S. and the average academic performance in the U.S. is closely correlated with economics. The richest Americans are also much richer than the average Americans. Those two facts are likely tied together in important ways. The question facing America (which is the closely tied to the same political question which divides our two parties and their philosophy) is whether to measure success by the best or by the most. In the U.S. you get two different answers for both economics and education. --Jayron32 13:48, 13 September 2017 (UTC)[reply]
Yes, wealth distribution is very important, particularly for education in the USA, where funding and access to education tends to be locally controlled, and thus segregated by wealth, socio-economic status, race, etc. Most of our states in the USA have world-class schools for rich kids. Few of our states manage to provide good education for the poor. SemanticMantis (talk) 16:07, 13 September 2017 (UTC)[reply]
Sure, it's more than just providing more resources to rich kids, but providing more resources to rich kids is definitely a problem, and it happens all over the county [3], if not your county. Even if your county spends equally per pupil, the linked map shows that a) it is well behind the USA's national average and b) the children in the counties to your left will have more money spent on them. I completely agree that evaluating based solely on student performance is problematic. While it is true that poor students' learning depends less on teaching quality than middle or rich kids, quality of resources and educators still matters. I think there's a case to be made for spending more per-pupil on the poor kids, as equal funding is apparently not leading to equitable outcomes, but I won't be holding my breath (e.g. this [4] famous illustration). SemanticMantis (talk) 18:29, 13 September 2017 (UTC)[reply]
...yes, if the spending more per pupil means sending them to boarding schools, and away from their dysfunctional homes. StuRat (talk) 18:42, 13 September 2017 (UTC)[reply]
(Congrats on the longest link I've ever seen.) I suspect that a lack of reading in poor homes causes the regression. However, I don't suspect that lack of money causes lack of reading but more the other way around. Households that don't encourage reading and other learning have kids who grow up to be poor and continue to discourage learning. Apparently kids watching Housewives of <insert random city here> isn't the rocket straight to the top we all assumed it would be. StuRat (talk) 18:19, 13 September 2017 (UTC)[reply]
The BBC is running an investigation on why summer born children achieve less than children born at a different time of the year, a disadvantage which continues throughout life [5]. I've not been following (the series is called Whodunnit: The Calendar Conspiracy) but I assume it's to do with the fact that the school year begins on 1 September, which means that summer born children are the youngest in the class. The effect is also explored in Malcolm Gladwell's book Outliers[6] but the parameters are slightly different. The remaining programmes air at 13:45 BST on Radio 4 tomorrow and Friday and you can catch the whole series on iplayer. 92.8.216.51 (talk) 20:17, 13 September 2017 (UTC)[reply]
Tuition fees for US universities are astronomical, it's of the order of a year's income. But students obviously are not getting anything close to a personal tutor, so they are in fact paying for the wages of the top researchers. Count Iblis (talk) 08:41, 14 September 2017 (UTC)[reply]
Actually, the increase in U.S. tuition isn't paying for non-teaching researchers. The recent trend in university staffing is to reduce the number of researchers (teaching and non-teaching) and increase the number of non-tenure track teachers who don't do research (and cost less to pay). So if universities are reducing the higher-paid researchers and replacing them with non-tenure track instructors, why is tuition raising at such an astronomical rate? It's to pay administrators. The majority of the cost increases of non-profit university tuition (both public and private) in the U.S. is born solely by the increasing cost of paying the salaries of newly created administrative positions (aka bureaucracy). The other cost increases are caused by a decrease in state funding of tuition; the amount that the state pays for student education both in relative and absolute (inflation adjusted) amounts has decreased sharply.this article from the New York Times and This more detailed article from the statistics site 538.com explain it well. The NYT article focuses more on the administrative costs; while 538 places more blame at the foot of decreased state support. Either way, nearly ALL analysis (either these two or any of a dozen other studies and articles on the subject) clearly don't support your thesis that the increase in tuition is born by converting teaching positions to research positions. The trend is to go in the OTHER direction, actually as shown in this article here, to wit, "[since the 1980s] the variety within non-tenure-track, full-time faculty has expanded, as many faculty members who were once on the tenure track have been moved to term contracts." --Jayron32 11:22, 15 September 2017 (UTC)[reply]
.jpg)