. 如图所示,位于竖直平面内的固定光滑圆环轨道与水平面相切于 M 点,与竖直墙相切于 A 点,竖直墙上另一点 B 与 M 的连线和水平面的夹角为 60 °, C 是圆环轨道的圆心,已知在同一时刻: a 、 b 两球分别由 A 、 B 两点从静止开始沿光滑倾斜直轨道分别沿 AM 、 BM 运动到 M 点; c 球由 C 点自由下落到 M 点.则 ( )
【简答题】The best example of universally understood body language may be smile. A smile can help us get through difficult situations and find friends in a world of strangers. A smile can open doors and tear do...
【简答题】Fill in each of the blanks in the following sentences with a word listed below. Change the form where necessary. occurrence tighten behavior disturb accomplishment desperate awkward release option squ...