图示杠杆机构中B处为螺栓联接,材料许用切应力为 [img=99x25]1803de02f231be6.png[/img],不考虑挤压,已知支座B处约束力为[img=112x27]1803de02fc4c349.png[/img] ,则螺栓最小直径为( )。[img=2362x780]1803de030ae168e.png[/img][img=2362x780]1803de0319c96e7.png[/img]
A: d =18 mm
B: d =15.2 mm
C: d =17.7 mm
D: d =18.4 mm
A: d =18 mm
B: d =15.2 mm
C: d =17.7 mm
D: d =18.4 mm
举一反三
- 图示杠杆机构中B处为螺栓联接,材料许用切应力为 [img=99x25]18034cea6257314.png[/img],不考虑挤压,已知支座B处约束力为[img=112x27]18034cea6b558a9.png[/img] ,则螺栓最小直径为( )。[img=2362x780]18034cea78a1ffc.png[/img][img=2362x780]18034cea86b0611.png[/img] A: d =18 mm B: d =15.2 mm C: d =17.7 mm D: d =18.4 mm
- 图示杠杆机构中B处为螺栓联接,材料许用切应力为[img=89x25]18034cea01b918a.png[/img] ,不考虑挤压,已知支座B处约束力为 [img=112x27]18034cea0a8206d.png[/img],则螺栓最小直径为( )。[img=2362x780]18034cea1e33c36.png[/img] A: d =18 mm B: d =15.2 mm C: d =17.7 mm D: d =18.4 mm
- f(x)在x处可导,a,b为常数,则[img=27x32]1802fa0c04c2042.png[/img][img=234x25]1802fa0c10631ae.png[/img]= A: [img=93x26]1802fa0c195a7ad.png[/img] B: [img=93x26]1802fa0c2233a71.png[/img] C: [img=39x26]1802fa0c2adc024.png[/img] D: f(x)
- 设随机变量X服从均值为2的指数分布,X的分布函数为F(x),数学期望为E(X),方差为D(X),则以下结果正确的是 A: [img=128x28]1802d3b369ab5fe.png[/img] B: D(X)=4 C: P(X<2︱X>1)=F(1) D: P(X>2︱X>1)= F(1) E: [img=112x27]1802d3b372fb534.png[/img] F: D(X)=E(X) G: P(X≤2︱X>1)= F(2) H: [img=82x27]1802d3b37bbbf05.png[/img]
- 设随机变量X服从均值为2的指数分布,X的分布函数为F(x),数学期望为E(X),方差为D(X),则以下结果正确的是 A: [img=128x28]18034b986fbc78a.png[/img] B: D(X)=4 C: P(X<2︱X>1)=F(1) D: P(X>2︱X>1)= F(1) E: [img=112x27]18034b98781508a.png[/img] F: D(X)=E(X) G: P(X≤2︱X>1)= F(2) H: [img=82x27]18034b9880d080a.png[/img]