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1140347986314533
2 năm trước
một khẩu pháo có khối lượng M=450kg nhả đạni theo phương nằm ngang. Đạn pháo có khối lượng m=5kg, vận tốc ban đầu của nó khi ra khỏi nòng là v=450m/s. Khi bắn, hẹ pháo giật về phía sau một đoạn s=9cm. tìm lực cản trung bình tác dụng lên pháo
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