giúp mình với ạ 1/Một hòn đá có khối lượng 50g được ném lên từ mặt đất với vận tốc 10m/s. Lấy g=10m/s2 . Bỏ qua mọi ma sát và lực cản trong không khí. a. Tính trong hệ qui chiếu gắn với mặt đất các giá trị động năng, thế năng, cơ năng của vật tại mặt đất và tại độ cao 0,5m so với mặt đất. b. Tính vận tốc hòn đá khi lên đến độ cao 3,75m. c. Tính độ cao cực đại vật đạt được. d. Khi rơi lại đến mặt đất, hòn đá lún sâu vào đất đoạn 2cm. Tính lực cản trung bình của đất tác dụng vào đá.

Các câu hỏi liên quan

II. Chuyển các câu sang phủ định và nghi vấn: 1. Her mother wrote a sick note for her ........................................................................................................................... ........................................................................................................................... 2. Nam was absent from school yesterday. ........................................................................................................................... ........................................................................................................................... 3. I had a bad cold two days ago. ........................................................................................................................... ........................................................................................................................... 4. Many students caught flu last month. ........................................................................................................................... ........................................................................................................................... 5. They were happy with their life. ........................................................................................................................... ........................................................................................................................... 6. He suggested going out for dinner. ........................................................................................................................... ........................................................................................................................... 7. I was busy last Sunday. ........................................................................................................................... ........................................................................................................................... 8. We enjoyed our summer vacation ........................................................................................................................... ........................................................................................................................... III. Đặt câu hỏi và trả lời với would like: 1. Nam/ pineapple ........................................................................................................................... ........................................................................................................................... 2. she/ have cucumber salad for dinner ........................................................................................................................... ........................................................................................................................... 3. your brother/ something to drink ........................................................................................................................... ........................................................................................................................... 4. they/ fried fish, boiled spinach and some potato soup ........................................................................................................................... ........................................................................................................................... 5. you/ play some games of chess ........................................................................................................................... ........................................................................................................................... 6. Hoa’ uncle/ some spinach and cucumber

1. Thu’s father reads a morning newspaper everyday, ___________? 2. The teacher is going to explain a new grammar lesson, ___________? 3. Their classmates were so excited about the games yesterday, ___________? 4. Lan enjoys sewing clothes for her doll, ___________? 5. Hoa did a lot of homework last night, ___________? 6. Schools may be closed if it snows heavily, ___________? 7. She has visited the citadel in Hue twice, ___________? 8. People have to rebuild the building after fire, ___________? 9. Their children enjoy playing computer games, ___________? 10. You will have a cable TV soon, ___________? 11. I am making a big mistake, ___________? 12. Let’s go shopping at Saigon Coop Mart, ___________? 13. Children should drink a lot of milk and fruit juice, __________? 14. Bring your camera with you to the party, ___________? 15. These shoes need to be fixed, ___________? 16. You must ask for your parents’ permission to join in the trip, ___________? 17. Ba likes healthy food, ___________? 18. Thu didn’t take part in the competition, ___________? 19. Phong hasn’t been to Hanoi before, ___________? 20. She can ride to school by herself, ___________? 21. My friends are used to swimming in the river, ___________? 22. His mother doesn’t work for that company, ___________? 23. They don’t have to buy new dictionaries, ___________? 24. It will rain tomorrow, ___________? 25. Remember to buy your mother some sugar on your way home, ___________? 26. She has read this news on the internet, ___________? 27. They have seen lots of Beckham’s pictures on his website, ___________? 28. You think Internet is a means of education, ___________? 29. There was a lot of traffic in the streets yesterday, ___________? 30. You ought go now, _______________? 31. I think she won’t come to your party, _______________? 32. What a nice dress, ___________? 33. It is time for you to study hard, ______________? 34. You need go right now, _____________? 35. He need never study hard, _________________? 36. You think it is going to rain, __________________? 37. He said that his father was a doctor, _______________? 38. Everything is all right, __________________? 38. She met nobody at the party, _________________? 39. Don’t forget to turn off the lights before going out, __________________? 40. Be careful with that man, _________________? 41. Luciano Pavarotti is a great singer, ___ ___? 42. It isn't very cold today, ___ ___? 43. Ms. Patton assigns a lot of homework, ___ ___? 44. I didn't bring enough money, ___ ___? 45. The children won't want to go to bed early, ___ ___? 46. You have already seen Brave heart, ___ ___? 47. The movie received several Oscars ___ ___? 48. We can't keep our dog in the hotel room, ___ ___? 49. The Braves would like to win another World Series , ___ ___? 50. Basketball players don't have small feet, ___ ___? 51. All can’t speak at a time,______________? 52. Everyone cheered wildly, __________________? 53. Very little progress has been made, __________________? 54. A few people knew the answer, __________________? 55. We could scarcely hear what he said, __________________? 56. He went nowhere else, __________________? 57. Let’s go to the cinema, __________________? 58. Don’t talk in class, __________________? 59. You have heard about that, _________________? 60. He used to beat his wife, ________________? 61. She could scarcely hear what he said, ______________? 62. They did nothing, ________________________? 63. There is no one in the house, _______________? 64. A little progress has been made, __________________? 65. The child rarely cries, __________________? 66. You have never in the house, __________________? 67. There’s an examination tomorrow, ______________? 68. So you don't think I can do it, __________________?. 69. Well, I couldn't help it , __________________? 70. She said that her father was a famous scientist, __________________?