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biiginzofficial
2 năm trước
Tính công do lực kéo và lực ma sát thực hiện khi 1 vật trượt đều trên mặt sàn nằm ngang với vận tốc 4 m/s trong thời gian 60 giây dưới tác dụng lực kéo F = 20 N trong 2 trường hợp: a) Lực vecto F hợp với phương ngang 1 góc 30 độ. b) Lực vecto F nằm ngang.
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Các câu hỏi liên quan

A. GRAMMAR I. Choose the best option. 1.They_________the bus yesterday. A. don’t catch B. weren’t catch C. didn’t catch D. not catch 2. My sister_________home last night. A. comes B. come C. came D. was come 3. My father_________tired when I _________ home. A. was – got B. is – get C. was – getted D. were – got 4. What_________you_________two days ago? A. do – do B. did – did C. do – did D. did – do 5.Where_________your family_________on the summer holiday last year? A. do – go B. does – go C.did – go D. did – went 6. We_________David in town a few days ago. A. did see B. was saw C. did saw D. saw 7. It was cold, so I_________ the window. A. shut B.was shut C. am shut D.shutted 8. I_________to the cinema three times last week. A.was go B. went C. did go D.goed 9.What_________you_________last weekend? A.were/do B.did/did C.did/do D.do/did 10.The police_________on my way home last night. A. was stop B.stopped C.stops D.stopping 11. The film wasn’t very good. I_________ it very much. A.ẹnjoyed B.wasn’t enjoy C.didn’t ẹnjoyed D. didn’t enjoy 12.The bed was very uncomfortable. I_________sleep very well. A.didn’t B.did C.wasn’t D.not 13. The window was opened and a bird_________into the room. A.fly B. flew C. was flew D.did fly 14. I_________a lot of money yesterday. I_________an expensive dress. A.spend/buy B.spent/buy C.spent/bought D.was spent/bought. III. Complete the sentences with the correct form of the verb in brackets. 1. Which sports you (play) at the weekends? 2. My brother (buy) 2 tickets for the table tennis match yesterday. 3. Last weekend I (play) with my friends and we (have) a very good time. 4. Nowadays many girls (like/do) aerobics to keep fit. 5. What time you (arrive) at the stadium? 6. How often he (go/fish) ? 7. your team (win) yesterday? 8. My sister (play) badminton twice a week. He (do) it on Saturday and Sunday. 9. Where you (go) on holiday last year? 10. I (cycle) 100 kilometers last week. IV: Write meaningful sentences, using the simple past 1. It/be/cloudy/yesterday. ……….……….……….……….……….……….……….……….……….………. 2. In 1990/we/move/to another city. ……….……….……….……….……….……….……….……….……….………. 3. When/you/get/the first gift? ……….……….……….……….……….……….……….……….……….………. 4. She/not/go/to the church/five days ago. ……….……….……….……….……….……….……….……….……….………. 5.How/be/he/yesterday? ……….……….……….……….……….……….……….……….……….………. 6. Mr. and Mrs James/come back home/and/have/dinner/late/last night? ……….……….……….……….……….……….……….……….……….………. 7. They/happy/last holiday? ……….……….……….……….……….……….……….……….……….………. 8. How/you/get there? ……….……….……….……….……….……….……….……….……….………. 9. I/play/football/last/Sunday. ……….……….……….……….……….……….……….……….……….………. 10. My/mother/make/two/cakes/four/days/ago. ……….……….……….……….……….……….……….……….……….……….

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