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На двух вертикально расположенных пружинах одинаковой длины горизонтально подвешен стержень. Жесткости пружин k1 = 0,02 Н/м и k2 = 0,03 Н/м, расстояние между ними d = 1 м. В каком месте стержня нужно подвесить груз, чтобы стержень остался в горизонтальном положении? Массой стержня пренебречь.
Задача 4.
К источнику постоянного напряжения 200 В подключена схема из четырех резисторов, как показано на рисунке. На двух резисторах выделяется мощность 50 Вт, на других двух - 100 Вт. Как изменятся эти мощности, если замкнуть ключ К?
b) Answer the following questions.
1. What kind of animals were used for work during the Bronze Age?
2. What were the first wheels hike?
3. What are the stages in the development of the wheel?
4. How many people did the first steam carriage carry?
5. Who demonstrated the first locomotive in the United Kingdom?
6. Was the Russian government interested in railway transportation?
7. Who were the Cherepanovs?
8. What was the first Russian locomotive like?
9. Are the locomotives widely used in Russia?
10. What kind of locomotives are used in Russia now?
Текст 7. DIFFERENT KINDS OF LAND TRANSPORT
1. What was the reaction of the people after the invention of the steam engine?
In Washington the story is told of a director of the Patent Office who in the early thirties of the last century suggested that the Office be closed because "everything that could possibly be invented had been invented". People experienced a similar feeling after the invention of the steam engine.
But there was a great need for a more efficient engine than the steam engine, for one without a huge boiler, an engine that could quickly be started and stopped. This problem was solved by the invention of the internal combustion engine.
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