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tthao2412
2 năm trước
1. Người ta phải thực hiện 1 công 3000J để đưa 1 vật lên cao 2 m bang mpn dài 20m với hiệu suất là 80 % a) Xác định trọng lượng vật b) Tính công để thang lực ma sát khi kéo vật đi hết mpn ? c) Tính độ lớn của lực ma sát ?
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