[Archive!] Pure mathematics, physics, chemistry, etc.: brain-training problems not related to trade in any way - page 68

 
joo писал(а) >>

Can that software simulate a sphere with an internal mirror surface and a light source in the centre...?

What do you need it for, if it's not a secret? Are you inventing a fusion reactor?

 
Richie >>:

А зачем вам это нужно, если не секрет? Термоядерный реактор изобретаете?

Just curious. It will probably heat up the air inside and with it the bulb gradually. Which will melt first, the glass of the bulb or the glass of the mirrored sphere? :)

Even if we assume that the bulb doesn't generate heat.

 
Mathemat >>:

Сила инерции? Я такой не знаю. Но если послушать, что говорит VladislavVG, то в принципе это можно понять. Но это все же, если уж говорить точнее, не сила инерции, а просто равнодействующая сил, приложенных к материальной точке.

Центробежная сила? Ну это ж фикция, возникающая при переходе к неинерционной системе отсчета. Сила есть одна - центростремительная.

Sorry, but that's not correct. This is beyond the scope of the Statics section .

The force of inertia is part of the net force applied to a material point and is due to the presence of acceleration - in diphysics, describing dynamics, it is a coefficient representing mass multiplied by the 2nd derivative. If you compose the balance of forces equation of a moving system without considering it, you will not get zero, so the system of equations will not have a solution - or rather there will be infinitely many of them.

The centripetal force arises as an equilibrating force to the centrifugal force - it does not exist by itself - otherwise the body would tend to the point around which the instantaneous rotation occurs.

Elementary - why does a car in a turn tilt to the side opposite to the turn ? Explain ;) ? And also under what conditions does side slip occur ? And why ?


Good luck.

2 Yurixx Are you familiar with the discipline of theoretical mechanics?
 
joo писал(а) >>

Just curious. It will probably heat up the air inside and with it the bulb gradually. Which will melt first, the glass of the bulb or the glass of the mirrored sphere? :)

Even if we assume that the bulb doesn't give off any heat.

Alas, it is impossible to simulate heating there. If you take the bulb's coil as the point in the centre of the sphere, the coil should melt first.

By the way, if you are not aware, large spherical bodies are capable of heating themselves - for example planets.

 
VladislavVG >>:

1. Сорри, но это не верно. Может это потому, что дальше раздела "Статика" Вы механику не изучали ?

2. Сила инерции, это часть равнодействующей сил, приложенных к материальной точке и обусловлена наличием ускорения - в дифурах, описывающих динамику это коэффициент, представлющий массу, умноженный на 2-ю производную.

3. Центростремительная сила возникает как уравновшивающая к центробежной - сама по себе не существует - иначе тело бы стремилось к точке, вокруг которой происходит мгновенный поворот.

4. Элементарно - почему авто в повороте наклоняется в сторону, противороложную повороту ? Объясните ка ;) ?

1. studied further, and so was theor-mechanics (but not too much, as my speciality is related to electronic engineering).

2. I have an idea about diphures describing dynamics. But you've convinced me that I'm wrong: it's even more fiction than I assumed. Here's the wiki article (pardon the mauvais ton).

3. There, in the same article, it also says about centrifugal force. And it's a fiction, as it's also a force of inertia (but I knew that a long time ago).

4. elementary. Just because there is a force that makes it turn. And it is this force that is primary.

 
Richie >>:

Кстати, если вы не в курсе, то большие сферические тела способны разогреваться сами - например планеты.

I am aware of that. But the nature of this phenomenon is different from the one I made the assumption about.

 
Mathemat писал(а) >>

Mathemat, do you believe in gravitons? It's a continuation of the fly thread ....

joo wrote >>

I know.

But the nature of this phenomenon is different from the one I made an assumption about.

Heating up of large spherical bodies is an interesting thing, sheds light on a lot of things :)

 
Mathemat >>:

1. Изучал и дальше, и теормех тоже был (но не слишком много, т.к. моя специальность связана с электронной техникой).

2. Я имею представление о дифурах, описывающих динамику. Но Вы меня убедили, что я не прав: это даже больше фикция, чем я предполагал. Вот статья в вики (извините за моветон).

3. Там же, в той же статье, написано и о центробежной силе. И это фикция (но об этом я знал давно).

4. Элементарно. Как раз потому, что есть сила, заставляющая его поворачивать. И именно эта сила первична.

Why do you think the need has arisen? Precisely because there is an effect. Regarding inertial reference systems - this is as much a fiction (as the concept of "force" itself) - a very strong simplification (like a spherical horse in a vacuum). Can you give an example of at least one inertial system (Earth is not one of them)? By the way in the same article it is written that centrifugal forces exist, but nothing about centripetal - probably because it is not primary.

on p.3 and what is this force? where is it directed and where is it applied?

Good luck.

 
Richie >>:

Mathemat, а вы в гравитоны верите? Это я в продолжении темы про мух ....

Well yes, quite ready to admit the existence of particles providing gravitational interaction (if I don't confuse them with gravitino). But not so categorical as to believe either.

2 VladislavVG: well, one can go so far as to declare anything as fiction. Let's not argue about terms and quarrels. You know exactly what we are talking about. And you won't name me a perfectly inertial system, nor will I. But that doesn't stop Newtonian physics from working very well not only on Earth, but also in, say, the solar system.

P.S. By the way, Newtonian physics is also protected from non-inertiality of the system - just by these fictitious forces.

 
Mathemat >>:


2 VladislavVG: ну так можно докатиться и до того, чтобы объявить фикцией что угодно. Давайте лучше не будем спорить о терминах и ссориться. Вы прекрасно понимаете, о чем речь. И Вы так же, как и я, не назовете мне идеально инерциальную систему. Но это не мешает ньютоновой физике работать очень неплохо не только на Земле, но и, скажем, в Солнечной системе.


So I'm not trying to quarrel - it's not constructive at all. I simply tried to show that there are effects, which cannot be explained (calculated) without introduction of corresponding assumptions (even fictions), at least within modern mechanics.

And about reference frames 100%. Such systems are simply not yet known.

Good luck.