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Физика ! Срочно !!! Если у кого-то есть тетрадь для к/р работ по физике 7 класс, напишите пожалуйста к/р номер 4 ( по главе 5 в уч.) все варианты , кроме 1 ! Буду очень благодарна! Дам 15 баллов за всё !
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Могу сказать решения 6 и 7, они лёгкие. 8 не могу, там не всё условие.6 ЗАДАЧА:КПД= A полезная/ A затраченная. Тк это подвижный блок, мы выигрываем в силе в 2 раза, но проигрываем в расстоянии в 2 раза ( золотое правило механики). A полезн= mgh. А затраченная= F (некая сила, неважно какая) * 2h (тк сливаем в расстоянии в 2 раза). 120*10=1200-mg. (1200h)/2hF. h сокращаются, получается 1200/2f. Вспоминаем, что КПД=0,8. Следственно, 1200/2f=8/10. Откуда 16F=12000, F=750.Ответ: 750 H7 ЗАДАЧА: V балки= S попереч сеч* длину = 0,01м^2*5м=0,05м^3.Ро стали= 7800 кг/м3. Ро=m/V, m= Ро*V= 7800*0,05=390 кг. Mg=3900H. A= F*S, A=mgh= 3900*10=39000Дж= 39КДЖОтвет: 39 КДЖ
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Автор:
gavynf6qu - 5 лет назад
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Переведите пожалуйста
THE WILD GEESE OF CANADA
One year I lived in the northern part of Canada, near a blue lake, with green trees all around. That part of Canada is also the home of the wild geese, and I longed to hear their "honk." When the wild geese come, it means that the snow will soon melt, and the game will be back in the brown hills, that the winter is over and the warm, bright days will be here. This is the message that the honk of the wild geese, flying in the sky, brought to our ancestors thousands of years ago, and this is the message that I waited for.
I wanted to hear the call of the honkers. But there were no wild geese on my lake, so I brought a pair of blacknecks from another lake, and they made their nest on a little island on my lake. Soon, in a bed of soft gray down, lay six great ivory eggs. The patient mother sat on them four weeks without rest, except in the afternoon, when she left them for half an hour. And round and round that island the gander swam about, like a war-ship on patrol. I tried to land and see the nest one day. The goose sitting on the eggs quacked to warn the gander of danger. There was a long, sharp hiss, and before my boat could touch the shore, the gander was between me and the island and faced me, ready to fight. Evidently, I could land on their island only over his dead body. So I left them in peace.
At last the six shells opened, and six golden chicks peeped out. The next day they left the nest, — the mother first and the chicks close behind her, and last the father. This order they always kept. The mother always leads, and the father follows — yes, obeys. And what a brave guard he was! The gander will fight anything alive, if his little ones are in danger, and there are very few animals or birds of his size that can face him.
So the flock grew big and strong. In three months they were almost as big as the old ones. In four months their wings were strong enough to fly. Their voices were still small and thin, and they did not yet have the deep honk of the older geese. Then they began to make short flights across the lake. As their wings grew stronger, their voices became deeper and deeper.
Soon the thing I dreamed of happened, — the flock of wild geese flew up into the air and "honked". But each time they came back to their home water that was also mine. Now their flights were longer and higher. But they always came back to the lake.
One day, at the end of September, when the leaves began to fall, flocks of small birds flew over the lake. Above them were flocks of wild geese from the far north on their way to the warm south, and I heard their loud "honk". The wild geese on my lake looked up and answered, and at once began to line up on the lake. Their mother led the way, swimming fast and faster. Then she quacked, then called and then their voices rose. "Honk, honk!" they cried, and they flew away to join the other honkers in the southern sky.
"Honk, honk, honk!" they shouted as they flew. But — what! The mother was not in the line. She still splashed on the surface of the lake. And now their loud "On, on! Come on!" was answered by the mother, and the father too, — "Come back! Come back!" So the young ones returned, splashing down on the lake at the call of the mother.
"What is it?" they called all together, as they swam about. "Why don't we go? What's the matter, mother?" The mother could not tell. She only knew that when she gave the signal for all to fly, she could not rise with the rest. The young ones rose, but the old ones, their strong leaders, could not rise.-
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