Treo một vật vào một lực kế thấy lực kế chỉ 30N
a)Hãy phân tích các lực tác dụng vào vật.Nêu rõ điểm đặt,phương,chiều và độ lớn của các lực đó
b)Khối lượng vật là bao nhiêu?

Một vật có khối lượng m=4,5kg buộc vào 1 sợi dây.Cần phải giữ dây bằng một lực bao nhiêu để vật cân bằng?

IX. Fill in the blanks with suitable Impositions: in, at, on, after, under, between, beside, among, out of, above, beneath

19. There is a bus station ______ the end of this road. 

20. Keep those medicines ______ the children's reach.  

21. I lost my keys somewhere ______ the car and the house.   

22. Come ______ and sit ______ your sister.   

23. D comes ______ C in the alphabet.   

24. The boat sank ______ the waves.  

25. Don't shelter ______ the trees when it's raining. 
26. Please put these books ______ the bookshelf ______ the desk.  

27. I often feel nervous when I am ______ strangers.  

28. Children must attend school ______ the ages of 5 and 16. 

II. Fill in the blanks with mustn't or don't/ doesn't have to.

37. They ______ work on Saturday. 
38. Visitors ______ feed the animal.  

39. Tim ______ wear uniform at school.  

40. You ______ touch that switch. It's very dangerous. 
41. Don't make so much noise. We ______ wake the Baby.  

42. There's a lift in the building, so I ______ climb the stairs.  

43. Staff ______ smoke when serving customers.  

44. Sally is extremely rich. She ______ work.  

45. I don't want anyone to know about our plan. You ______ tell anyone.  

46. You ______ be a good player to enjoy a game of tennis.  

I. Complete the sentence with must or have/ has to. Sometimes both are possible.

11. Oh, it's later than I thought. I ______ go.  

12. She's a really nice person. You ______ meet her.  

13. You can't turn right here. You ______ turn left.  

14. You ______ do something.  

15. I haven't phoned Lisa for ages. I ______ phone her tonight.  

16. I ______ get up early tomorrow. There are a lot of things I want to do.

17. My eye sight isn't very good. I ______ wear glasses for reading.  

18. Van Lam can't come out with us this evening. He ______ work.  

19. It's 11 o'clock. I ______ go now.  

27. I'm afraid I can't go with you. I ______ learn for my next exam.  

28. Tomorrow is our public holiday so we ______ get up early.  

29. You ______ think over before answering my questions.  

30. I'm a new comer here so I ______ ask direction to everywhere.  

31. You ______ put the sharp things out of children's reach.  

32. Vietnamese children ______ wear uniform when they go to school.  

VII. Complete the sentences, using reflexive pronouns with the verbs in the box.

(burn –  look after – decorate – paint – defend – buy - think of - pay for - turn off - help)

1. I don't want you to pay for me. I'll ______. 

2. Some people are very selfish. They only ______. 

3. Be careful! That pan is very hot. Don't ______. 

4. The computer will ______ if you don't use it.
5. Let's ______ the house______.
6. Don't worry about Jane and me. We can ______. 

7. Who decorated the Christmas tree? The children ______ it ______. 

8. Joanna ______ these gifts ______.
9. If you want more to eat, ______, children.

10. If someone attacks you, you need to be able to ______.