Một con lắc lò xo dao động điều hòa theo phương thẳng đứng trùng với trục của lò xo được giữ cố định, đầu phía dưới của lò xo gắn vào một đĩa cân nhỏ có khối lượng \({m_1} = {\rm{ }}400{\rm{ }}g\). Biên độ dao động của con lắc lò xo là 4 cm. Đúng lúc đĩa cân đi qua vị trí thấp nhất của quỹ đạo, người ta đặt nhẹ nhàng lên một vật nhỏ có khối lượng \({m_2} = {\rm{ }}100{\rm{ }}g\) lên đĩa cân m₁. Kết quả là ngay sau khi đặt m­₂, hệ chấm dứt dao động. Bỏ qua mọi ma sát. Bỏ qua khối lượng của lò xo. Biết\(g{\rm{ }} = {\rm{ }}{\pi ^2} = {\rm{ }}10{\rm{ }}m/{s^2}\). Chu kỳ dao động của con lắc khi chưa đăt thêm vật nhỏ \({m_2}\)  bằng

REDUCED RELATIVE CLAUSES:

1. The next train which leaves the station is to London.

2. The road which connects Hanoi and Ho Chi Minh city is called Number 1

3. The man who sat next to me on the train looked gentle.

4.. The steam engine which was invented by James Watt opened a new period in human

development history.

5. I felt sorry for Paul, who was the only child on the block.

6. The car which is running quickly is red color

7. The boy has a ball which he kicks everyday.

REDUCED RELATIVE CLAUSES:

27. The next train which leaves the station is to London.

28. The road which connects Hanoi and Ho Chi Minh city is called Number 1

29. The man who sat next to me on the train looked gentle.

30. The steam engine which was invented by James Watt opened a new period in human

development history.

31. I felt sorry for Paul, who was the only child on the block.

32. The car which is running quickly is red color

33. The boy has a ball which he kicks everyday.

34. We leam English which we want to have better communication with other people

35.I was born in Hanoi, which is the capital of Vietnam

36. We have an apartment which overlooks the park.

37. The ideas which are presented in that book are interesting.

38. Are national parks good places that can house wild animals?

39. The next question that they will consider is how to clean up the garbage.

40. The noise which comes from the boat engine might disturb sea animals