Một vật có khối lượng 50kg đang chuyển động với vận tốc 54km/h thì hãm phanh chuyển động thẳng nhanh dần đều. Sau 10s vận tốc 18km/h a) Độ biến thiên của động năng và động lượng b) Lực hãm phanh có độ lớn là bao nhiêu c) Quảng đường vật đi đc trong thời gian trên d) Sau đó đụng vào 1 vật có khối lượng 5kg đg đứng yên .Sau va chạm 2 vật dính lại và chuyển động cùng 1 vận tốc .Tính vận tốc của 2 vật sau khi va chạm .

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X. Read the passage and choose the correct answer Television is very popular and even has some benefits for kids. It helps very young children learn the letters of alphabets and helps other kids learn about science, cultures, and world events. However, researchers show that too much TV is bad for children. For one thing, there is a link between watching more than four hours of TV a day and being overweight. For another thing, many TV shows are violent and upsetting. Watching these shows may cause kids to be more fearful. And of course, more time in front of the TV means less time to study. Too much TV also be the cause of lower grades. Experts don’t agree on the solution to the problems. Some say that kids should watch only educational programs; others say kids should watch no TV at all. And others suggest teaching them to watch TV as occasional entertainment, not as an every day hobby. 1. What is the passage mainly about? A. Benefits of kids’ TV shows B. effects of TV on kids C. why kids love TV D. why kids shouldn’t watch TV 2. According to the passage, watching a lot of TV may ____ A. Cause weight problems in children C. cause children to be more famous B. Cause children to get better grades D. cause students to study more 3. The word “them” in paragraph 3 is closest in meaning to A. Programs B. experts C. kids D. problems 4. The word “occasional” in paragraph 3 is closest in meaning to A. Very often B. not very often C. always D. every day 5. What can be inferred from the passage? A. TV is always bad for children C. TV is only good for entertainment B. Kids should watch only educational shows D. television has some benefits along with problems