Thí nghiệm đã chứng tỏ rằng mỗi ròng rọc động làm giảm lực kéo hai lần so với kéo trực tiếp vật lên. Bỏ qua khối lượng ròng rọc. Khi kéo vật M có khối lượng 120 kg lên cao nhờ palăng (gồm 2 ròng rọc cố định và 2 ròng rọc động). Thì lực kéo đầu dây có cường độ nhỏ nhất là: A. 1200N B. 800N C. 600N D. 300N Mình đang cần gấp ạ

Các câu hỏi liên quan

Exercise 4. Complete the sentences with a/an, some or any. 1. I want __________ orange juice. 2. There 's _________ charity shop in the community. 3. Is there ________ sugar in the kitchen? 4. Tom's just bought _________ English book on robots. 5. They have got __________ food left for the winter. Exercise 5. Write sentences, using the words given. 1. She/ 13 years old/ ,and /she/ now/grade 8. ______________________________________________________________________ 2. She/have/ younger brother/,and/ his name/ Bruce Walkers. ______________________________________________________________________ 3. My father/ work/ our farm / the countryside. ______________________________________________________________________ 4. How many /orange/ there / the bag? cheapest fry most chopsticks rest waiter at care menu peel ______________________________________________________________________ 5. Ao dai / usually /wear / young women. ______________________________________________________________________ 6. Some students /offered /scholarships / study /abroad. ______________________________________________________________________ 7. My mother /do/ the housework/, and /she/ help/ the farm. ______________________________________________________________________ 8. It / easy/ find/ apartment / Ha Noi. ______________________________________________________________________ 9. The puppets /support/by /strings /under/ water. ______________________________________________________________________ 10.I / looking/ forward to/ see/ you/ there. _____________________________________________________________________