题目内容：
直径为d的圆截面钢材受轴向拉力作用已知其中纵线应变为ε，弹性模量为E, 则杆的 轴力为___________A.πd2ε/4E
B.πd2E/4ε
C.4Eε/πd2
D.πd2Eε/4
参考答案：
选择题：直径为d的圆截面钢材受轴向拉力作用已知其中纵线应变为ε，弹性模量为E, 则杆的 轴力为_______
- 题目分类：华北水利水电大学材料力学
- 题目类型：选择题
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A.πd2ε/4E
B.πd2E/4ε
C.4Eε/πd2
D.πd2Eε/4
A.πd2ε/4E
B.πd2E/4ε
C.4Eε/πd2
D.πd2Eε/4
设X1,X2,…,X6是来自N(u,02)的样本,S2为其样本方差,则DS2的值为( A)1/3 o
设X1,X2,…,X6是来自N(u,02)的样本,S2为其样本方差,则DS2的值为( A)1/3 o 4. : ( B ) 1/5fo . : ( C)2/5
已知F0.1(8,20)=2,则F0.9(20,8)=1
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