[Archive!] Pure mathematics, physics, chemistry, etc.: brain-training problems not related to trade in any way - page 51
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ЗАДАЧА на засыпку №2 (очень простая):
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В теплоизолированный сосуд насыпали 1 кг поваренной соли, потом присыпали 1 кг ментола, потом присыпали 1 кг снега. Содержимое сосуда хорошо перемешали. Вопрос: Как изменится температура содержимого сосуда через несколько минут?
I studied inorganic chemistry a long time ago. There are some salts that, when dissolved in water, if their concentration is high enough, lower the temperature by 30 degrees (endothermic reaction). It seems that saltpeter belongs to such salts (it is wonderfully soluble in water, several times better than table salt).
I don't know what menthol has to do with it all, but the whole mixture will probably get seriously cold, i.e. turn into salted ice with a strong menthol taste.
Here, in the third paragraph, it even says about regular salt.
But there are no special paradoxes in this problem: it's just the trivial dissolution of salt in water.
OK, I'll answer the 2nd question, but let the "public" think for themselves for now.
Yurixx wrote correctly, the freezing temperature of the mixture decreases, but he is wrong in that the salt and snow mixture heats up. It doesn't heat up, it cools down. As it cools it absorbs energy from the outside environment. Such a mixture has a lower freezing point. Try mixing 50g of salt with 50g of snow in a glass, the temperature of the mixture will be much lower after a while. As for the menthol - it has no effect on anything.
I studied inorganic chemistry a long time ago. There are some salts that, when dissolved in water, if their concentration is high enough, lower the temperature by 30 degrees (endothermic reaction). It seems that saltpeter belongs to such salts (it is wonderfully soluble in water, several times better than table salt).
I don't know what menthol has to do with it all, but the whole thing should freeze, as it will seriously cool down.
Here, in the third paragraph, it even says about common salt.
Yeah, you're right. People usually think that salt melts snow, but it turns out it cools it down. Saltpetre also refers to such substances, and for example, the fixative for developing photographic materials (sodium thiosulphate) and many other substances. Most of them are very water soluble indeed.
Под скоростью шасси вы понимаете окружную скорость колёс шасси? Почему же не взлетит?
Jesus, why are you and Yuri so clever!? I'm not even offended by the crap you wrote. But you'll have to answer for MAI! :о) Get it right - it will not take off. For one simple reason - read the problem statement. I don't know how to technically implement these conditions, but it won't take off. It's written in the conditions. The only way to meet them is to hold the plane in place, and to do that, the conveyor belt has to rotate with a tremendously high acceleration. I don't remember all calculations exactly (and I won't even repeat them), but acceleration of conveyor belt should add up to couple, three km/sec^2. I don't remember, maybe less, maybe even a little less.
In theory this variant does not fly. Practically - it is impossible to check, because of the lack of the required transporter.
If you cannot understand - simply remember, this condition - does not fly :o)
There are several variants of this problem, this variant does not fly. If the speed of the transporter was equal to the speed of the plane, then yes, easily, there would be no problem at all. But read the problem statement. That's it! Honestly, I'm fed up. Good luck inventing a time machine. It's better not to go in here, it's like a drug. It's like a time killer and what's it for?
PS: Yuri, I didn't expect such dickishness from you. Honestly - I didn't expect it.
With intrigue? No problem:
Question: Can a heater consume 1 kW of electricity and still produce 1.5 kW of heat?
If the speed of the transporter was equal to that of the aircraft
Did you mean the speeds of the undercarriage wheel and the belt?
Let me remind you of the condition:
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Swetten wrote >>
An aircraft (jet or propeller) is standing on a runway with a moving cover (like a transporter). The pavement can move against the plane's take-off direction, i.e. towards it. It has a control system that monitors and adjusts the speed of the runway so that the speed of the wheels of the aircraft is equal to the speed of the runway.
Question: would the aircraft be able to spread out on this belt and take off?
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If the speed of the transporter were equal to that of the aircraft, it would stand still and never take off.
С интригой? Нет проблем:
Вопрос: Может ли отопительный прибор потреблять 1 кВт электроэнергии, а выделять при этом 1,5 кВт тепла?
Of course it can. You take a powerful kilowatt light bulb, screw it to a bucket of firewood and plug it into the mains. It'll draw exactly one kilowatt from the mains. The whole system will generate more, as the wood will also be burning.
Of course it can. You take a powerful kilowatt light bulb, screw it to a bucket of firewood and plug it into the mains. It'll draw exactly one kilowatt from the mains. And the whole system will give out more, because the wood will be burning too.
I apologize for the inaccurate wording of the question. No firewood. No fire, gas, coal, uranium, etc. We plug the appliance into the socket, it consumes 1kW and gives 1.5kW of heat.
С интригой? Нет проблем:
Вопрос: Может ли отопительный прибор потреблять 1 кВт электроэнергии, а выделять при этом 1,5 кВт тепла?
Yes