Câu 4. a, Giải thích vì sao các tấm tôn lợp nhà thường có hình lượn sóng? b, Tại sao tháp Epphen bằng Thép ở Pháp về mùa hè cao hơn mùa đông? C, Tại sao khi hơ nóng quả cầu bằng kim loại thì quả cầu không bỏ lọt vòng kim loại? (hình 18.1 SGK trang 58) d,Tại sao khi được nhúng vào nước lạnh thì quả cầu lại lọt qua vòng kim loại? (hình 18.1 SGK trang 58)

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