A. He broke his leg. B. He has caught a cold. C. He has a stomachache. D. He has a toothache. 7. A. At 2 o'clock this afternoon. B. At 3 o'clock this afternoon. C. At 10 o'clock this morning. D. At 10 o'clock tomorrow morning.
【简答题】如图所示,一对带电平行金属板 A 、 B 与竖直方向成 30° 角放置 .B 板中心有一小孔正好位于平面直角坐标系 xOy 的 O 点, y 轴沿竖直方向 . 一比荷为 1.0×10 5 C/kg 的带正电粒子 P 从 A 板中心 O' 处静止释放后沿 O'O 做匀加速直线运动,以速度 v 0 =10 4 m/s ,方向与 x 轴正方向成 30° 角从 O 点进入匀强电场,电场仅分布在 x 轴的下...