离心泵密封环和叶轮配合处的每侧径向间隙一般应为叶轮密封环处直径的()。
A.0.10%~0.15%
B.0.15%~0.20%
C.0.05%~0.10%
D.越小越好
参考答案:D
在投影图中,为了表示物体内部、外部的形状常用剖面图和截面图来表示,因此()。
A.当形状具有对称平面时,可以对称轴线画成半剖视图来表示物体的内外结构
B.为了反映物体的内部、外部的形状均可以画成半剖视图来表示
C.为了反映物体的内外结构,可以画成全剖视图来表示
D.全剖视图能反映物体的内外结构
Cars X and Y were traveling together on a straight road at a constant speed of 55 miles per hour when car X stopped for 5 minutes. If car Y continued to travel at 55 miles per hour, how many minutes from the time that car X resumed traveling did it take car X traveling at 60 miles per hour to catch up with car Y ?() (Assume that the time for car X to slow down and speed up was negligible.)
A.5
B.30
C.45
D.55
E.60