[Archive!] Pure mathematics, physics, chemistry, etc.: brain-training problems not related to trade in any way - page 23
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Whatever the flies do in a flying aircraft, its mass does not change.
Это обычная статика. Внутренняя энергия тут ни при чем. Есть элеиентарное условие равновесия сил. На весы давит вес самолета и воздух внутри него. А за счет чего мухи летают ? Что компенсирует их вес ? Воздух. Они опираются о воздух своими крылышками. Так что воздух давит на весы с силой вес+сила давления мух.
I have two objections:
1. Air doesn't weigh anything, as we weigh in the same air (Archimedes' force).
2. Similarly, according to Bernoulli's law (is it?), flies, when they fly, do not push their wings downwards, but in all directions.
Whatever the flies do in the flying plane, its mass does not change.
2 Richie: What does a flying plane have to do with anything?
Yes, the mass does not change, but it is redistributed within the system. This means that the weight must also change.
Взлетит ли самолет с тонной летающих в нём мух, если в момент/моменты отрыва от земли они будут одновременно садиться?))
No, it won't take off, the pilot must be deceased, otherwise where would the flies come from? :-))Yuri, have you ever tried walking up an escalator to meet the movement of the belt? Do you accelerate much? You don't take off? :о))) (kind of a joke)
Tried it. It's my favourite thing to do. It goes up much faster (especially in St. Petersburg) than standing stupidly on what's going up.
У меня два возражения:
2. Аналогично, согласно закону Бернулли (ему?), мухи, когда летают, давят своими крылышками не вниз, а во все стороны.
Flies don't fall where ?
down
they're pushing downwards.
Пробовал. Это мое любимое занятие. Получается забежать наверх значительно быстрее (особенно в СПб), чем если тупо стоять на том, что едет вверх.
There aren't that many flies in St. Petersburg.
Things are better here
I have two objections:
1. Air doesn't weigh anything, as we weigh in the same air (Archimedes' force).
2. similarly, according to Bernoulli's law (is it?), flies, when they fly, do not push their wings downwards, but in all directions.
1. absolutely correct. However, don't forget - both air weighs and Archimedes' force acts (and not just on the air inside, but on the plane and the flies).
2. oops ... Why then, when they stop flapping their wings they fall down and not in all directions ? :-)
Юрий, ты пробовал когда нибудь на эскалаторе идти на встречу движению ленты? Сильно ускоряешься? Не взлетаешь? :о))) (это типа шутка)
For the purity of the experiment, we also need rollers on the legsМухи не падают куда ?
вниз
значит давят вниз
Nope, in all directions. By the time the air disturbance from the wings reaches the wall, it has time to reach all the other walls.