Câu 28: Chọn câu trả lời sai Một người đi xe đạp trên đoạn đường MNPQ. Biết trên đoạn đường MN =S1 người đó đi với vận tốc v1, trong thời gian t1; trên đoạn đường NP =S2 người đó đi với vận tốc v2, trong thời gian t2; trên đoạn đường PQ =S3 người đó đi với vận tốc v3, trong thời gian t3. Vận tốc trung bình của ngươì đó trên đoạn đường MNPQ được tính bằng công thức. A. v =v1+v2+v3/3 , v=s1+s2+s3/t1+t2+t3 , v=v1t1+v2t2+v3t3/t1+t2+t3 , D. Cả B, C đều đúng

Các câu hỏi liên quan

I. Mark the best answer A, B, C or D to complete these sentences below. 1. The ethical implication of laboratory scientific __________ on animals is an issue discussed worldwide. * 1 điểm A. experiments B. tools C. experiences D. devices 2. The dependency to computers displayed in the behavior of certain people is called computer __________. * 1 điểm A. addicting B. addiction C. addiction D. addicted 3. Science and technology have __________ the life safe, secure and comfortable. * 1 điểm A. transformed B. made C. done D. changed 4. With the advance of the science and technology, our life changes greatly in various __________ . * 1 điểm A. scenes B. fields C. sights D. regions 5. Generally speaking, most technology has had a__________ effect on our lives. * 1 điểm A. benefit B. benefice C. beneficial D. beneficent 6. It remains to be seen what the __________ impact of this technology will be. * 1 điểm A. long B. long-term C. boring D. relax 7. Few __________ have had a greater influence on mankind than the computer. * 1 điểm A. invent B. inventors C. inventions D. inventing 8. It is undeniable that __________ have revolutionized our lives. * 1 điểm A. computers B. computer C. computerizing D. computed 9. The 21st century has already seen considerable__________ in computer technology. * 1 điểm A. progress B. progressing C. progresses D. process 10. It is not easy to predict how this __________ is going to develop. * 1 điểm A. technique B. technology C. technologies D. technologizing

I.Khoanh tròn từ có cách phát âm đuôi ed khác với các từ còn lại 1. a. filled               b. missed                 c. ploughed                          d. watched 2. a. visited           b. decided                c. engaged                            d. disappointed 3. a. kissed              b. stopped                   c. laughed                             d. closed 4. a. reformed        b. appointed                c. stayed                               d. installed 5. a. fitted               b. educated                 c. locked                               d. intended 6. a. matched          b. educated                 c. enriched                            d. washed 7. a. attended         b. improved                 c. dedicated                         d. exhibited 8. a. killed             b. developed               c. threatened                        d. endangered 9. a. wanted            b. looked                     c. needed                              d. visited 10. a. planned         b. worked                    c. helped                               d. galloped 11. a. hoped                b. referred                   c. shopped                            d. laughed 12. a. hurried                b. studied                    c. stayed                               d. started 13. a. watched              b. passed                     c. used                                  d. washed 14. a. moved                 b. hoped                      c. married                             d. danced 15 a. retired                 b. escaped                   c. faded                                d. played 16. a. believed            b. asked                       c. allowed                             d. died 17. a. called              b. phoned                    b. showed                             d. finished 18. a. fired               b. traveled                   c. enjoyed                             d. decided 19. a. apologized     b. explored                  c. rained                               d. wondered 20. a. spilled               b. opened                    c. finished                            d. climbed 21. a. failed                 b. believed                   c. stopped                             d. solved 22. a. liked                    b. laughed                   c. earned                               d. missed 23. a. admitted      b. deleted                    c. controlled                         d. intended 24. a. jumped             b. robbed                     c. closed                               d. enjoyed 25 a. amassed           b. raided                      c. invented                           d. collected 26. a. experimented      b. collected                  c. needed                              d. raised 27 a. selected           b. obtained                  c. afforded                           d. collected 28. a. added                  b. subtracted               c. hooked                             d. visited 29. a. mixed                  b. raised                       c. delayed                             d. closed 30 a. supposed             b. collected                  c. admired                            d. posed