写单词,补全句子。(每空一词)
A: ____ he usually have breakfast at seven o'clock?
B: No, but he____ breakfast at seven yesterday.
﹣3的倒数是( )
如图所示,在固定的圆锥形漏斗的光滑内壁上,有两个质量相等的小物块A和B,它们分别紧贴漏斗的内壁. 以各自不同的水平速度在不同的水平面上做匀速圆周运动,则以下叙述正确的是( )