Một người kéo một vật từ giếng sâu 8m lên đều trong 20 giây. Người ấy phải dùng một lực F=180N. Tính công và công suất của người đó. 

Một người dùng cái cung tên để bắn một con chim. 

      a) Khi giương cung (dây cung căng) thì cái cung có cơ năng không? Cơ năng ấy ở dạng        nào?

      b) Khi bắn, mũi tên bay vút đi, năng lượng đã được chuyển hóa như thế nào?

Để kéo một thùng hàng có trọng lượng 300N lên cao 10 mét bạn An phải mất thời gian là 1 phút. Tính công suất của bạn An?  

ð  If Carol ……………………………………………………

1.      Rita is exhausted today because she didn’t get any sleep last night.

ð  If Rita ………………………………………………………

2.      She’s very thin; perhaps that’s why she feels cold so much.

ð  If she …………………………………………………….

3.      He never polishes his shoes, so he never looks smart

ð  If he ……………………………………………………..

4.      He can’t park near his office; that’s why he doesn’t come by car

ð  If he ……………………………………………………..

5.      My house is guarded by two big dogs. That’s the only reason it isn’t broken into every night

ð  If my house …………………………………………………………

6.      The flats are not clearly numbered, so it is very difficult to find anyone.

ð  If the flats …..………………………………………………………..

7.      I don’t know her e-mail address, so I can’t tell you

ð  If I …………………………………………………………………….

8.      She works in the evening. She has no time to play with her children

ð  If she ………………………………………………………………….

9.      I don’t want them to be upset, so I’ve decided not to tell them what happened.

ð  They ……………………………………………………………..

10.  I am not tall enough to join the basketball team

ð  If I ……………………………………………………………………

11.  He doesn’t see the signal so he doesn’t stop his car

ð  If he ………………………………………………………………….

12.  Peter gets bad marks because he doesn’t prepare his lessons well

ð  If Peter ………………………………………………………………

13.  Mary doesn’t have enough money. She can’t buy a new car.

ð  If Mary ………………………………………………………………

14.  Go right now or you’ll be late for the train.

ð  If you………………………………………………………………….

15.  He doesn’t apply for the job because he doesn’t have enough qualifications.

ð  If he ………………………………………………………………….

16.  Hurry up, or we will be late for the exam.

ð  If we …………………………………………………………………

17.  They do not understand you because you do not often talk to them.

ð  If you …………………………………………………………………

18.  Because you speak English unnaturally, they do not understand you.

If you …………………………………………………………………

1.      She doesn’t live in London because she doesn’t know anyone there

ð  She’d ……………………………………………………………….

2.      I can’t live in the country because I can’t find a job there

ð  I’d  ………………………………………………………………..

3.      I don’t have a spare ticket. I can’t take you to the concert

ð  If I ………………………………………………………………...

4.      The schoolchildren sowed some seeds, but they forgot to water them so they didn’t grow.

ð  If the children ………………………………………………………..

5.      They don’t understand the problem. They won’t find a solution

ð  If they …………………………………………………………….

6.      He sits around too much. He isn’t fit.

ð  If he ………………………………………………………………

7.      Carol didn’t answer the phone because she was studying..

1.      If the earth suddenly (stop) …………. spinning we all (fly) …………. off it.

2.      If you (smoke) …… in a non-smoking compartment the other passengers (object) ……

3.      (your parents / not / be) ………………. proud if they could see you now?

4.      I’m broke, but I (have) ………….. plenty of money now if I (not / spend) ………… so much yesterday.

5.      If we (work) ……………all right, we (finish) ……………in time; but we have no intention of doing it

6.      If we (have) …………….. a submarine now, we (use) …………it to investigate the seabed

7.      Were he ten years younger, he (take) …………….. part in the voyage around the world

8.      Should you come late, they (not let) ……………… you in

9.      He might get rid of his cough if he (not smoke) ……………so much

10.  If someone (give) …………….you a boat what you (do) …………… ?

11.  Water (freeze) ……………. if the temperature falls below zero

12.  I (warn) ………….. you if I had seen you last week

13.  He always says hello if he (see) ………… you

14.  What would you do if he (resign) …………….. tomorrow?

15.  I wouldn’t have been so upset if Judy (write) ……………… to me earlier

16.  Shout if you (see) …………..anything unusually

17.  The engine starts if you (turn) ……………..this key

18.  If he weren’t so bad-temperature, his wife (not leave) …………….him so soon after the marriage

19.  What (you / say) ………………….if I offered you a job?

20.  The children always (get) ………….frightened if they watch horror films

21.  If it (not be) _____________ for you, I would be late

22.  I can’t help feeling sorry for the hungry children. If only there (be) __________ peace in the world

23.  Were I to become president, my first act (be) __________ to help the poor

24.  If he (listen) _____________ to his father’s advice, he would still be working here.

25.  If she hadn’t stayed up late last night, she (not / be) ____________ tired now.

26.  I feel as if my head (be) ___________ on fire now, doctor.

27.  He always talks as though he (address) ____________ at a public meeting.

28.  It was our fault to keep you waiting so long. We (inform) ___________  you in advance.

29.  Had I known her address, I (go) _____________ to visit her.

30.  He looked frightened as if he (see) _____________ a ghost.

31. If we meet at 9:30, we (have) __________ plenty of time.

32. Lisa would find the milk if she (look) __________ in the fridge.

33. The zookeeper would have punished her with a fine if she (feed) __________ the animals.

34. If you spoke louder, your classmates (understand) __________ you.

35. Dan (arrive) __________ safe if he drove slowly.

36. You (have) __________ no trouble at school if you had done your homework.

37. If you (swim) __________ in this lake, you’ll shiver from cold.

38. The door will unlock if you (press) __________ the green button.

39. If Mel (ask) __________ her teacher, he’d have answered her questions.

40. I (call) __________ the office if I (be) __________ you.

41. If they (listen) __________ carefully, they might hear the woodpecker.

42. If I had lain down on the sofa, I (fall) __________ asleep.

43. Ngoc could have worked as a model if she (be) __________ taller.

44. The soil (not/dry out) __________ if you water the plants regularly.

45. If you (give) __________ the young boy this stick, he’d hurt himself.

46. We (not/take) __________ the wrong tram if Dung had asked the policewoman.

47. If the cat hides in the tree, the dog (not/find) __________ it.

48. The students would have solved the problem if they (use) __________ their textbooks.

49. If he washed his feet more often, his girlfriend (visit) __________ him more often.

Manh (read) __________ the newspaper if he went by train

21.               If the weather (be) __________ nice, they (play) __________ football.

22.               If we (go) __________ to a good restaurant, we (have) __________ a better dinner.

23.               If An (learn) __________ more words, he (write) __________ a good report.

24.               If the boys (take) __________ the bus to school, they (arrive) __________ on time.

25.               If the teacher (explain) __________ the homework, I (do) __________ it.

26.               If they (wait) __________ for another 10 minutes, they (see) __________ the pop star.

27.               If the police (come) __________ earlier, they (arrest) __________ the burglar.

28.               If you (buy) __________ fresh green vegetable, your salad (taste) __________ better.

29.               If Alex (ask) __________ me, I (email) __________ the documents.

30.               If he (speak) __________ more slowly, Peggy (understand) __________ him.

11. If I (come) __________ home earlier, I (prepare) __________ dinner.

12. If we (live) __________ in HCMC, my boyfriend (visit) __________ us.

13. If Tung and Thanh (be) __________ older, they (play) __________ in our football team.

14. If he (be) __________ my friend, I (invite) __________ him to my birthday party.

15. If Xuan (study) __________ harder, she (be) __________ better at school.

16. If they (have) __________ enough money, they (buy) __________ a new car.

17. If you (do) __________ a paper round, you (earn) __________ a little extra money.

18. If Minh (get) __________ more pocket money, he (ask) __________ Lam out for dinner.

19. If we (win) __________ the lottery, we (fly) __________ to London.

If I (meet) __________ Brad Pitt, I (ask) __________ for his autograph

. Biết công suất của động cơ ôtô là 400kW làm việc với thời gian 2 giờ . Tính công của động cơ ôtô .