Hai con lắc lò xo M và N giống hệt nhau, đầu trên của hai lò xo được gắn trên cùng một giá đỡ nằm ngang. Vật nặng của M và N dao động điều hòa theo phương thẳng đứng với biên độ lần lượt là A và A√3. Trong quá trình dao động, chênh lệch độ cao lớn nhất giữa hai vật là A. Chọn mốc thế năng tại vị trí cân bằng của mỗi vật. Khi động năng của M cực đại và bằng 0,16 J thì động năng của N là Làm đi mn

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VIII. Read the text. Dear cousins, I'm here in England on a three-month exchange visit. It doesn't snow much in winter, so I don't have to wear lots of clothes like at home. The school is always quite warm because there's central heating. There are three floors, so I often get lost and have to ask for directions! DT is on the ground floor, for example, but biology is on the top floor – that's a lot of stairs! One good thing is that the doors on each floor have a different colour, so it's easy to remember: blue, red and green. The school subjects here aren't the same as at home. In history classes, we learn about English history, not European history, so I'm not very keen on that. We don't have to do economics this month because the teacher's sick (I can't stand economics!). But the science labs are brilliant! We can do lots of experiments, and the teachers are fun. Life outside the school is a big change! I have to be careful in the streets because cars all drive on the left. There's a good bus service between the town and the school, so I don't have to walk much. And the family I'm living with are very friendly. They have a son and a daughter about the same age as me, so we sometimes go out together. But there's still a lot that I don't understand! I have to do a lot of homework, so I don't watch much TV. And the food – what can I say about the food? They eat everything out of cans and packets, so I really miss my Mum's cooking! Write back soon! Guido Choose the correct answers. 1. Guido says he often needs ____________. A. clothes B. heating C. directions 2. The different colours help him to remember the ____________. A. classrooms B. floors C. subjects 3. Guido likes the ____________ classes. A. economics B. history C. science 4. Guido's main problem outside the school is the ____________. A. buses B. cars C. family 5. Guido wants to ____________. A. finish his homework B. eat his mum's food C. watch more TV