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MeoChuPi89
2 năm trước
Trên thực tế, ngoài việc dùng mặt phẳng nghiêng để kéo vật lên cao nhằm mục đích được lợi về lực, người ta còn dùng mặt phẳng nghiêng trong việc di chuyển vật từ trên cao xuống thấp như lăn cái thùng phuy từ trên sàn xe ô tô xuống đất. Trong trường hợp này, mặt phẳng nghiêng có tác dụng gì?
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Các câu hỏi liên quan

Bài 13: Đặt câu hỏi cho các cụm từ được gạch chân dưới đây. 1. Minh usually takes exercises after getting up. 2. I brush my teeth twice a day. 3. Nga has an appointment at 10.30 this morning. 4. They live in the city center. 5. I like “Tom and Jerry because its very interesting. 6. She is worried about the next examination. 7. Music makes people different from all other animals. 8. They do their homework at night. 9. I like the red blouse, not the blue one. 10. That is an English book. 11. He studies piano at the university. 12. My father is a teacher. 13. My favorite musician is Trinh Cong Son. 14. We take a holiday once a year. 15. It takes four hours to get there. 16. He earns a hundred pounds a week. 17. This book is 30.000 dong. 18. The car is expensive. Bài 14: Hoàn thành câu sau sử dụng các liên từ “although/ because/ but/ so”. 1. ___________ Norway is a beautiful country, it is very cold in winter. 2. It is warm and sunny today ___________ we are going to the beach. 3. The car is very old ___________ it is reliable. 4. Today is my daughters birthday, ___________ I need to buy her a present. 5. You should take an umbrella ___________ it is going to rain. 6. The camera is expensive ___________ it is very good. 7. I love chips ___________ it is not healthy. 8. His mother is not feeling well, ___________ he needs to take care of her. 9. Your marks in English are low ___________ you dont study hard enough. 10. ___________ he is a good ski instructor, I dont like him very much. 11. Id like to go with you ___________ Im too busy right now. 12. There are no buses this hour, ___________ we need to catch a taxi. 13. ___________ it rains a lot in winter, I like walking the dog in the park. 14. He fails his driving test, ___________ he needs to do it again. 15. We invite them to the party ___________ they dont want to come. 16. I dont like the concert ___________ the band doesnt play well. 17. We dont go on holiday ___________ we don’t have a lot of money. 18. I want to buy a car ___________ I need it for my job. 19. I’m learning French ___________ I want to live in Paris. 20. ___________ he’s got a car, he never drives to work. Bài 15: Sắp xếp các từ sau để tạo thành câu hoàn chỉnh. 1. accident / an / she’s / in / because / hospital / she / had. 2. but / they / many / work / don’t / hours / they / have / money / much. 3. asked / Paul / me / question, / a / replied / I / so. 4. buy / I / peppers / potatoes. / and / tomatoes, 5. them / apple / can / have / an / or/ a / . / She / have / both /. / She / mango / cant / of 6. can / piano /./ Karthik / play / but / he / play / the/ cant / the/ violin 7. hard-working / is / but / her / is / lazy / . / She / very / brother 8. clever / is / and / beautiful / . / she 9. shirt / can / the / blue / or / take / green / shirt/ . / You / the 10. / am / sister / tall / I / short / . / My / is / but Bài 16: Đọc đoạn văn và trả lời câu hỏi. How can we keep our teeth healthy? Firstly, we ought to visit our dentist twice a year. He can fill the small holes in our teeth before they destroy the teeth. He can examine our teeth to check that they are growing in the right way. Unfortunately, many people wait until they have toothache before they see a dentist. Secondly, we should brush our teeth with a toothbrush and fluoride toothpaste at least twice a day – once after breakfast and once before we go to bed. We can also use wooden toothpicks to clean between our teeth after a meal. Thirdly, we should eat food that is good for our teeth and our body such as milk, cheese, fish, brown bread, potatoes, red rice, raw vegetables, and fresh fruit. Chocolate, sweets, biscuits and cakes are bad, especially when we eat them between meals. They are harmful because they stick to our teeth and cause decay. 1. How often should we visit our dentist a year? 2. What should we brush our teeth with? 3. What else we can use to clean between our teeth after a meal? 4. What kinds of food are good for our teeth? 5. What kinds of food are bad for our teeth?

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