泄槽纵断面宜采用单一的底坡;若坡度由陡变缓,()。
A.变坡处应由反弧段连接;
B.变坡处应由抛物线连接;
C.变坡处应由直线连接;
D.变坡处应由折线连接。
参考答案:A
用30cm的细线将质量为4×10-3㎏的带电小球P悬挂在O点,当空中存在水平向右,大小为1×104N/C的匀强电场时,小球偏转37°后处于静止状态。(sin37°=0.6,cos37°=0.8,g=10m/s2)
(1)分析小球的带电性质及带电量;
(2)求细线的拉力。
Professor Williams keeps telling his students that the future _____ to the well-educated.
A.belongs
B.is belonged
C.is belonging
D.will be belonged