Quả cầu khối lượng m=100g gắn ở đầu 1 lò xo nằm ngang, đầu kia cao lò xo cố định độ cứng của lò xo k=40N/m. Quả cầu có thể chuyển động k ma sát trên mp ngang. Từ vị trí cân bằng O, ng ta truyền vận tốc v0=1m/s theo phương ngang. Độ dãn cực đại của lò xo là bao nhiêu

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