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ngochuyen046535
2 năm trước
Một thùng hàng có khối lượng 150 kg được kéo lên theo một tấm ván dài 7,5m, cao 2,5m. Coi ma sát không đáng kể. a/Hỏi phải tác dụng vào thùng một lực F tối thiểu bằng bao nhiêu? b/Tính công mà F thực hiện.
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