[Archive!] Pure mathematics, physics, chemistry, etc.: brain-training problems not related to trade in any way - page 27

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joo >>:

Смотря с каким ускорением они подпрыгнут отталкиваясь от пола самолета. Получится тоже самое, что и в "задаче о мухах"

Here's the simplest example of a boy. The question is simple - To change or not to change. And how do you change?

 
All right, then. Here goes then. There are tiny particles hovering in the air around the plane, and Brownian motion prevents them from settling down on the plane. They weigh exactly 1t. Now consider how much the system as a whole would weigh if the plane were given an electrostatic charge so that the particles would settle on it. (ignore the mass of lost/gained electrons during electrostatic charge)?
 
Farnsworth >>:

Ну вот самый простой пример с мальчиком. Вопрос то простой - Измениться или нет. И как измениться?

I have hand-drawn a graph of the change in weight over time on page 25.

 
Richie >>:

Законы сохранения энергии и импульсов помните? Если пассажиры подпрыгивают, то в момент их отталкивания самолёт пойдёт вниз, не намного

конечно, т.е. вес его уменьшится на время. Когда они будут в нём парить (доли секунд) он действительно будет меньше весить, но они же не

взаимодействуют с ним, они присамолётятся. Когда они присамолётятся, вес самолёта снова вырастет и вернётся в первоначальное состояние.

Yes, I remember. And why then, according to your reasoning, the flies flying in won't change the scale?

 
Mathemat писал(а) >>

I'm serious too. Referring to experience will not help the problem. Once again: we are not talking about a helicopter, as the airflow from it is too powerful and almost unidirectional (almost however!). We are talking about small flies, of which there are a ton (that's ten million flies at a guess). They are all flying in different directions, flapping their wings. And the disturbance from the wing, even if it flapped strictly downwards, will still not go in a straight column downwards, but will scatter in all directions. The flies are in the gas, not lying flat.

You are correct, the flow is not in one direction, it is "pyramidal" blowing. The propeller under the action of the helicopter's mass is bending strongly in a cone.

By the way, this stabilises the helicopter a lot.

What is the total vector of all the flies? Zero. So, what are you saying, that they don't interact with the plane through the air of the plane?

 
Farnsworth писал(а) >>

Yes, I remember. And why then, according to your reasoning, the flies flying in would not change the scale?

Because the flies have interacted with the plane before - when they flew in it.

 
joo >>:

Я на 25-й странице изобразил от руки график изменения веса во времени.

y-axis - weight or some kind of "dynamics"?

 

Richie, they interact, but in all directions, on all the walls of the plane. It's almost the same molecules, just bigger a bit.

 
Farnsworth >>:

ось "y" - вес или какая то "динамика"?



pips
 
Richie >>:

Потому, что мухи взаимодействовали с самолётом и ранее - когда в нем летали.

i.e. they were pressing their one tonne into the air and that one tonne across the air was strictly pushing down?

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