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June 2

question related to chemistry

when a limited quantity of water is sprinkled over dirty white stone like substance a lot of heat and steam is evolved with hissing sound. after some time the stone like substance changes into white amorphous powder .

1) name and chemical formula of stone like substance 2)name the chemical formula of white amorphous powder 3)chemical equation for reaction takes place 4)what is the type of reaction 5)one use of amorphous powder — Preceding unsigned comment added by Kastumandonda (talk • contribs) 02:42, 2 June 2014 (UTC)[reply]

Please do your own homework.

Welcome to Wikipedia. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know.--Jasper Deng (talk) 03:02, 2 June 2014 (UTC)[reply]

It would be difficult to get a start on this homework if the OP has no idea about the identity of the stone-like substance. Obviously the first recommendation would be to read recent notes from lessons to identify this. Are we allowed to give a clue? Dbfirs 08:59, 2 June 2014 (UTC)[reply]

Heck - I'm sure there are many such substances but let's try quicklime. "Upon contact with water, quicklime would increase its temperature above 150 °C" 196.214.78.114 (talk) 10:00, 2 June 2014 (UTC)[reply]

Scientist

Is it true that scientist Nicola Tesla died a virgin? — Preceding unsigned comment added by Reburipos (talk • contribs) 10:50, 2 June 2014 (UTC)[reply]

Tesla never married, claiming that his chastity was very helpful to his scientific abilities. However he befriended a female pigeon and declared "I loved that pigeon as a man loves a woman, and she loved me.". See Nicola Tesla#Personal life. 84.209.89.214 (talk) 11:23, 2 June 2014 (UTC)[reply]

Ewwww!!! 24.5.122.13 (talk) 00:55, 3 June 2014 (UTC)[reply]

immortal

can we bring back a person back to life if we immediately store his body in liquid nitrogen? — Preceding unsigned comment added by 14.98.32.182 (talk) 12:01, 2 June 2014 (UTC)[reply]

No. See Cryopreservation and Cryopreservation#Risks 196.214.78.114 (talk) 12:55, 2 June 2014 (UTC)[reply]

"We" ? No. Future generations ? Perhaps. StuRat (talk) 12:57, 2 June 2014 (UTC)[reply]

There are two possible interpretations of what you just said:

A person that we freeze, today, might be brought back to life by a future generation.
A person that a future generation freezes might be brought back to life by either them, or some yet further into the future generation.

The first of those two seems unlikely. Freezing people in the way that we do now causes horrendous amounts of damage at the cellular level - this is unlikely to be repairable, ever. The second of the two is more likely - but whether you'd have to store the body in liquid nitrogen (as the OP specifies here), or in some other manner, is less clear. We've heard recently that patients who have serious injuries can sometimes be chilled down to relatively low temperatures by replacing their blood with cold liquids, and then revived with little ill-effect once the original injury has been repaired and their blood replaced. That's nothing like as cold a liquid nitrogen, it's not even below freezing - but it's a step in the right direction.

So I'd say "No" - not with liquid nitrogen alone. Perhaps with some other means of chilling the body - but not any way we know to do it now.

Also, it's unlikely we'd be able to make someone immortal that way - if someone is dying of old age, we freeze them, wait until we can fix whatever they are dying of - we probably can't fix all of the damage that's already done by all of the aging. We might very well be able to make people immortal by preventing them from ever aging...but that's easier than fixing the aging once it's happened.

But it's speculation - we don't know. SteveBaker (talk) 20:27, 3 June 2014 (UTC)[reply]

Bringing dead people back to life violates the Second Law of Thermodynamics. It will never happen. --AboutFace 22 (talk) 00:42, 4 June 2014 (UTC)[reply]

We don't know enough about the nature of life to make that blanket claim. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:50, 4 June 2014 (UTC)[reply]

"We don't know enough about the nature of life to make that blanket claim" We do. It will never happen! Read about respiratory chain, electron transfer and you will understand why. --AboutFace 22 (talk) 01:12, 4 June 2014 (UTC)[reply]

No, we don't know enough. We're just starting to get some clues. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:36, 4 June 2014 (UTC)[reply]

And what are those clues? --AboutFace 22 (talk) 15:39, 4 June 2014 (UTC)[reply]

Does some publisher/author pay for typos?

The only person I've ever heard of as paying for reports of mistakes (more serious than typos) in his books is Professor Donald Knuth, best-known as author of The Art of Computer Programming. Among computer scientists, he's so famous that the cheques he sends out often go uncashed - people would rather have proof they can hang on their wall that they found a mistake in one of his books.

Other than that, I have never heard of anybody who pays for reports of typos. They might be grateful for them, and conceivably it might be a way to convince them to give you a job as a proofreader, but that's about as far as it'll go.

Wouldn't it be feasible for a renowned publisher to pay some symbolic $0.xx amount at least? OsmanRF34 (talk) 13:26, 2 June 2014 (UTC)[reply]

I'm not familiar with any practice like that. While it might make sense in certain academic contexts, typos in most publications just don't matter that much. The cost of fixing is going to be much higher than the cost of finding, at least in traditional printed media. In related news, the Kindle lets you report typos in ebooks. I'm not entirely sure what happens to the reports, but I assume that they can be used to fix future editions. SemanticMantis (talk) 13:42, 2 June 2014 (UTC)[reply]

Spotting typos is the paid job of the proofreader. No publisher would pay random strangers for typo reports, otherwise they would be flooded with false positives from people who simply misunderstand what they are reading, or don't understand the subtleties of the language. When I was in publishing, we got far more letters and emails from people who misunderstood what they were reading than genuine typos.--Shantavira|^{feed me} 16:02, 2 June 2014 (UTC)[reply]

I'm struggling to see the relevance of this q to the Science desk. Humanities or Misc would seem to have been more obvious choices. -- Jack of Oz ^{[pleasantries]} 12:36, 3 June 2014 (UTC)[reply]

Hazards of helicopters hovering low

Is it safe for a small, simple helicopter to remain hovering and travelling about at 5 to 20 meters above the ground and mess around like that for 20 minutes? Anna Frodesiak (talk) 13:33, 2 June 2014 (UTC)[reply]

How small? A small single-seat vehicle, or a hexacopter? AlexTiefling (talk) 13:35, 2 June 2014 (UTC)[reply]

Other than the "obvious" hazard of an abrupt loss of power due to any number of causes, a potentially disastrous hazard of hovering is vortex ring state where the rotor suddenly loses lift as it descends into its own downwash. It's a hazard for any type or size of rotorcraft. Roger (Dodger67) (talk) 13:42, 2 June 2014 (UTC)[reply]

The nearer to the ground, the highest the risk of crashing against buildings. If the ground is flat, it's still a problem, if the pilot has to perform an emergency landing. OsmanRF34 (talk) 13:54, 2 June 2014 (UTC)[reply]

When a helicopter is within about 2 rotor-diameters of the ground, ground effects and Coandă effects start to strongly influence the behavior of the aircraft. Hovering over sloping ground - or close to an obstacle like a building or a tree - can result in sideways forces on the helicopter that can become hard to control...especially if more than one of them is 'in play' at any given time. The amount of lift generated by the rotors also changes drastically as you move into and out of ground effect - so flying at just above rooftop level will cause rapid variations in lift as you move over buildings and then over the open spaces between them. Overall, the pilot will be working hard to keep everything safe - so doing this for long periods might be fairly exhausting. SteveBaker (talk) 14:13, 2 June 2014 (UTC)[reply]

This is a normal part of helicopter training. For example, see Basic Flight Maneuvers in the Helicopter Flying Handbook, published by the FAA. Around here, it's very common to see Robinson helicopters training at the "grassy spot." At Palo Alto, where I fly, these pilots will be in controlled airspace and will need to be communicating with the Tower (air traffic control), even when they are so close to the ground. At a nearby airport, Hayward, there are (unofficial) airport charts showing helicopter maneuver areas and the pattern that they normally fly. Bear in mind that unlike fixed-wing aircraft, helicopters can operate at any altitude and change their direction of flight in x, y, or z (if authorized by the tower). Unpredictable! At my home airport, the helicopters usually do hover training south of the runway, and when they overfly the runway, they typically fly as if they were fixed-wing aircrafts.

During hover training, the pilots may dwell just a few feet above the ground, and are honing their ability to keep the aircraft stationary in various configurations, while working against various wind conditions. They may also be performing a hover taxi (as opposed to an air taxi, not to be confused with a Part 121 air taxi, a totally different technical term). Nimur (talk) 15:08, 2 June 2014 (UTC)[reply]

We have an article - Helicopter height–velocity diagram. As the chart illustrates, there are 'safe' and 'unsafe' airspeed/altitude combinations. Hovering higher than a few metres for any length of time is best avoided. With forward momentum, an engine failure is less risky, as the helicopter can more easily autorotate to a safe landing. AndyTheGrump (talk) 15:23, 2 June 2014 (UTC)[reply]

Vic Morrow might have a comment on this question if he were alive today. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:44, 2 June 2014 (UTC)[reply]

That is absolutely fascinating and very informative! The vortex ring state is very interesting, as is the Coandă effect. I never knew.

Just to let you know, the helicopter was a teeny, two-seat, probably single engine (as two would never fit inside).

It was mucking about like this over a flat, cement area around 80 x 80 metres by the seashore, with single storey structures, hedges and trees all around, no wind. A crowd of around 100 stood right at the edge the whole time watching, lots of kids, and there were thousands of people beyond walking by as it was Dragon Boat Day. It just didn't look safe.

Many, many thanks for the thoughtful reply. You know, this reference desk is the best kept secret on the Internet. Oh, and yes, poor Vic. He should have phoned SAC and his agent first. Anna Frodesiak (talk) 23:46, 2 June 2014 (UTC)[reply]

Re. the dead-man curve provided by AndyTheGrump: While operating in the shaded areas is indeed risky, many helicopter operations require operating in these areas -- the low-speed/medium-altitude area on the left of the chart is practically home ground for air-sea rescue, sky crane and other related operations, and the high-speed/low-altitude area on the bottom right is often visited by military helicopters that must fly fast and low to avoid getting shot down. 24.5.122.13 (talk) 01:03, 3 June 2014 (UTC)[reply]

Indeed it seems risky. Thanks for telling me what the red bar at the bottom of the chart is. I couldn't figure that out. Anna Frodesiak (talk) 06:57, 3 June 2014 (UTC)[reply]

Which is why choppers crash more often than planes -- simply because they're routinely required to fly in hazardous flight regimes as a normal part of their operations. 24.5.122.13 (talk) 10:06, 3 June 2014 (UTC)[reply]

...which in turn is kinda inevitable because fixed-wing aircraft are cheaper, safer and easier to fly - so anything you can do with a fixed-wing plane, you do. That leaves only the more dangerous/difficult missions for helicopters. SteveBaker (talk) 20:02, 3 June 2014 (UTC)[reply]

Protein amounts of True-Roots?

A nice Botanical question: Generally, how high is the protein content of True-Roots of plants? Can we generalize that it is higher from most other parts of the plant? (per cell). thanks. Ben-Natan (talk) 14:25, 2 June 2014 (UTC)[reply]

The protein content of plant roots is highly variable. Why would you think that roots are higher protein than other parts of the same plant? Are you interested in protein from a human nutrition perspective? If so, this page has a nice summary of root crops and comparison to other staples (in terms of % protein calories, which is different than per cell) [1]. Note that potato and yam have proportionally less human-available protein than wheat. Generally, seeds have a high protein content, compared to other parts of the plant, due to energy storage in the endosperm. Tubers are also storage organs, as are e.g. carrots. We tend to mostly eat roots that the plant uses to store energy, e.g. there isn't much nutrition in corn or wheat roots. SemanticMantis (talk) 19:35, 2 June 2014 (UTC)[reply]

I ask this from Curiosity and it's mostly based on intuition; I know that Seeds FE have high protein amount compared to other plant parts and I wonder what about roots.. I guess there isn't a simple answer as we have with seeds? thanks. Ben-Natan (talk) 05:41, 3 June 2014 (UTC)[reply]

Cat grooming

After watching my roommate's cat groom himself, I decided to read more about cat-grooming than I could find in Cat#Grooming, so I put <"cat grooming"> into Google — and all I get are pet stores and related businesses that will groom your pets for a price. Can someone explain why a cat would need grooming by a human? Nyttend (talk) 22:49, 2 June 2014 (UTC)[reply]

Well, there are many feral cats around the world which obviously don't need grooming by humans. But there are breeds of, particularly long haired cats, which were bred by humans for looks rather then "utility", which probably don't do so well without some assistance from humans. They either just look very shabby without human assistance, or in the worst case scenarios, they could ingest too much hair by grooming them selves which could lead to complications. Since humans generally don't want shabby looking or sick cats, their human slaves (owners) provide the grooming services. Vespine (talk) 00:18, 3 June 2014 (UTC)[reply]

A hairball usually doesn't make a cat "sick" in the American sense of the word (our British friends should read "ill" here), but it does make the cat sick in the British sense, which can be damaging to carpets. A cat in the wild presumably just coughs it up and goes on about its business, no harm done. --Trovatore (talk) 04:31, 3 June 2014 (UTC)[reply]

Yes, generally only long-hair cats need professional grooming, although short-hairs still need to be brushed or at least petted regularly to remove the bulk of the excess fur, to prevent fur balls. That system of licking themselves just doesn't seem very practical, to me, even for short-hairs, as they ingest far too much fur that way. StuRat (talk) 01:16, 3 June 2014 (UTC)[reply]

Also note that specialty cuts, like the one this cat received, are generally as unpopular with the owners as with this cat: [2]. StuRat (talk) 01:16, 3 June 2014 (UTC)[reply]

That's a lion cut. -- BenRG (talk) 04:20, 3 June 2014 (UTC)[reply]

Let's hope he got away from the groomer without a loin cut. :-) StuRat (talk) 04:10, 4 June 2014 (UTC) [reply]

Is there a place I can find the percent of rivers + lakes vs ocean on earth?

I am just a able to find the % when thinking in a 3d way (volume).201.78.203.91 (talk) 23:21, 2 June 2014 (UTC)[reply]

Are you looking for surface area instead of volume? --Jayron32 00:12, 3 June 2014 (UTC)[reply]

Rivers are a bit tricky, as they tend to vary in size with the season and weather. Lakes tend to be a bit more steady in size, and oceans more steady yet. StuRat (talk) 01:19, 3 June 2014 (UTC)[reply]

Please see Water distribution on Earth.--Shantavira|^{feed me} 08:39, 3 June 2014 (UTC)[reply]