Một vật có khối lượng 200g rơi tự do từ độ cao h = 20m, lấy g= 10m/s². Tính động năng của vật ngay trứoc khi vật chạm đất Tính động năng của vật khi nó ở độ cao 15m. Sau bao lâu động năng của vật bằng 20 J Một vật có khối lượng m = 1000kg chuyển động thẳng trên mặt phẳng ngang dưới tác dụng của lực F= 2000N hướng theo phương ngang. a.Tính công của F khi vật đi được quãng đường 100m b.Tính công của lực ma sát trên quãng đường đó. biết hệ số ma sát µ = 0,2. Giúp mình 2 câu này với

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Read this passage about the effect of visual pollution and answer the questions Visual pollution has a greater effect on people than you may think. I remember when I went to a foreign city, I was really scared because there was so much graffiti on the buildings' walls. Then I looked up and saw a lot of power lines over my head. Although they were not dangerous, I still felt insecure since I thought they might fall down. These things prevented me from enjoying the beautiful sights of the city. I also remember the time I studied in Melbourne. Once I was so busy with my assignments that I did not tidy my room for two weeks. Looking at the messy room caused me so much stress that I did not want to study. Then I decided to clean the room and put my things in their proper places. I also bought a small plant and placed it in a corner. These simple things actions increased my motivation and helped me to focus on my learning. 1. Why was the author scared when she was in a foreign city? → ________________________________________________________________________________________________ 2. How did the author feel when she saw the power lines? → ________________________________________________________________________________________________ 3. Why did she have that feeling? → ________________________________________________________________________________________________ 4. What was she busy with? → ________________________________________________________________________________________________ 5. What happened when she looked at the messy room? → ________________________________________________________________________________________________ 6. What did she do for her room? → ________________________________________________________________________________________________