Однородная цепочка длиной L лежит на гладком горизонтальном столе. Небольшая часть её свешивается в отверстие в столе. Лежащую на столе часть цепочки придерживают, но затем отпускают. Определить скорость цепочки в момент, когда длина свешивающейся части станет равна
Объяснение:
Newspapers and magazines play a very important part in our life. Practically there is no family that does not read them. We can learn many things from newspapers. Perhaps that is why many years ago an American humorous writer said: "All I know is what I see in the papers"; and another American author more than half a century ago wrote that "the careful reader of a few good newspapers can learn more in a year than most scientists do in their great libraries".
We can agree or disagree with these statements (better to disagree, because scientific books and magazines have more information than newspapers), but we'll have to say that newspapers help us in many ways. There are a lot of different kinds of newspapers in our country. One can buy them practically everywhere. It is impossible to read all the newspapers and magazines. Everyone has favourite ones.
My favourite newspaper is "Komsomolskaya Pravda". We can read almost about everything in this newspaper. There are articles dealing with home and abroad news, sport events, life of favourite actors and singers and even the weather. We can find many interesting things there. We can read some useful pieces of advice, some stories about our life, and so on. There are puzzles, songs and even anecdotes there. "Komsomolskaya Pravda" is one of the most interesting newspapers, to my mind.
не знаю как решать без массы, поэтому возьму тело массой 1 кг, тогда полная энергия в начальный момент будет равна кинетической энергии:
Ек.начальная=1/2*m*
=0.5*1*20*20=200Дж
теперь найдём на какой высоте потенциальная равна 1/2 общей энергии:
Еп=1/2Ек.нач.=200Дж/2=100Дж
Еп=mgh, отсюда
h=Еп/mg=100/1*10=10м
ответ : Еп=Ек на высоте 10 м.
проверим, найдем высоту на которую поднимется тело, брошеное со скоростью 20м/с
S=
=
=20м
а кинетическая равна потенциальной на половине пути 20м/2=10м, кстати это может быть и самостоятельным решением.