1 tên lua có m=500kg đang chuyển động vs v=200m/s thi khai hỏa.1 luong nhien leu co m=50kg cháy và phụt ra phía sau vs v=700m/s .a,tinh v của tên lửa khi phụt luong khí.b,sau đó phần vỏ của tên lửa chứa nhiên liệu m=50kg tách ra khỏi tên lửa chuyển động theo hướng cũ nhưng v giảm 1/3 .tìm v của tên lửa lúc đó

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Ex 1. Choose the suitable prepositions in brackets 1. Ba and Tam usually go fishing........................the weekends. (on, in, from, at) 2. The students will visit the capital.........................the summer. (on, in, at, of) 3. They heard a very strange noise............................midnight. (on, in, at, out) 4. Our little brother took a long nap from 1p.m.......4p.m. (till, up, between, at) 5. She talked........................an hour to persuade her parents. (in, for, at, up to) 6. They have learned English............many years. (since, for, in, from) 7. The boys often go skiing..........................the winter. (in, at, on, for) 8. I’ve studied French................................3 months. (for, since, in) 9. I arrived.......................the bus stop at 4 in the afternoon. (in, at, on, to) 10. We have lived in Hanoi............................4 years. (in, since, for, at) 11. She was born................................16th January. (in, of, at, on) 12. I’ve studied French................................last week. (for, since, in) 13. arrived at the bus stop at 4 ........................ the afternoon. (in, at, on, to) 14. What did she do ......................the weekend? (on, in, to, for) Ex 2. Rewrite sentences by using SO: 1. They could help you because they were not here. → …………………………........................................................................................ 2. I can’t go out because it’s raining. → …………………………........................................................................................ 3. This book is interesting enough for me to read twice. → …………………………....................................................................................... 4. There was fog. Their flight was delayed → …………………………........................................................................................ III. Join each pair of sentences using SO ….THAT 1. The holidays were very cheap. They booked one immediately → …………………………...................................................................................... 2. The plane was very late. They got to bed at three in the morning → …………………………..................................................................................... 3. The way to the beach was very long. It took them an hour to walk there → ………………………….................................................................................... 4. The beach was very crowded. There was hardly room to sit down → …………………………................................................................................... IV. Rewrite sentences 1. The water was very dirty. We decided not to go swimming. → The water was so ………………………….................................................... 2. She speaks English very well. You would thing it was her native language. → She speaks English so…………………………............................................. 3. The road is so narrow that it’s difficult for two cars to pass each other. → It is………………………….......................................................................... 4. The weather was so warm that I didn’t need a coat → It was…………………………......................................................................