1) выполним чертеж с указанием всех сил, действующих на маятник (он старый и к другой задаче, не смотрите на обозначения R и l. в целом он верен и подходит)
2) напишем уравнения динамики в проекции на вертикальную и горизонтальные оси
Tcosα = mg Tsinα = ma
разделим второе уравнение на первое. получаем, что
a = g tgα
3) из кинематики a = w² R. отсюда w = sqrt(a/R)
однако R - расстояние до оси вращения, и в данном случае оно равно R = l sinα, где l - длина нити (все-таки на чертеже эти обозначения пригодились). тогда
Преобразуйте предложения в косвенную речь.
1. “We live in a big city,’ they say.
2. “I am going to the market now,” Brian told her.
3. “I’ve found my passport,” Betty said
4. “I don’t like fish,” Ms Ford says.
5. Tom said: “I will help your sister.”
6. The dentist told me: “Don’t eat sweets anymore.”
7. The teacher said: “Keep the silence, please.”
8. John asked, “Have you seen the film?”
9. Tom asked, “Are you listening to music now?”
10. I asked, “Has she been working hard on this problem?”
11. She asked, “Was Nick in the library yesterday?”
12. He asked, “Does she work now?”
13. He asks, “Have you been reading this book since Friday?”
14. Jane asked, “Can anybody help me?”
15. He asked, “Will you be at Carol’s party tonight?”
16. “What have you bought me for Christmas?” the little boy asked his parents.
17. Helen said, “I cannot call you, I’ve lost your phone number”.
18. “Let’s go to a movie,” I said.
19. ‘’Why are you looking pale? What’s the matter?’’ asked Mother.
20. Ann asks Nina, “Where do you live?”