问题
问答题
对于许多高分子材料，其抗拉强度σb是数均相对分子质量
的函数：
式中，σ0为无限大分子量时的抗拉强度；A为常数。已知两种聚甲基丙烯酸甲酯的数均相对分子质量分别为4×104和6×104，所对应的抗拉强度则分别为107MPa和170MPa，试确定数均相对分子质量为3×104时的抗拉强度σb。
答案
参考答案：
解得
故
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对于许多高分子材料，其抗拉强度σb是数均相对分子质量
的函数：
式中，σ0为无限大分子量时的抗拉强度；A为常数。已知两种聚甲基丙烯酸甲酯的数均相对分子质量分别为4×104和6×104，所对应的抗拉强度则分别为107MPa和170MPa，试确定数均相对分子质量为3×104时的抗拉强度σb。
参考答案：
解得
故
It’s Sunday evening. I’m at birthday party. It is her birthday today. There many friends at house. Some stand beside the table and enjoy the food and drinks. I like the chocolate and the fruit . Sandy sits on the sofa and talks some friends there. She wears a new yellow T-shirt and ____blue jeans. She so cool. Wow! The cake is really big. All her friends begin to “Happy Birthday” to her. Then we share the big cake with her. Sandy is very at the party. Everyone has a good _______ here.
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