My little son asked ________.
A:that his father would come back in an hour
B:what's the matter with his sister
C:who could help him finish his homework
D:how long they had been to Wuxi
设想一:将煤油换成水来做实验,
设想二:通过加热空气来做实验.
如图,一充电后的平行板电容器的两极板相距l.在正极板附近有一质量为M、电荷量为q(q>0)的粒子;在负极板附近有另一质量为m、电荷量为﹣q的粒子.在电场力的作用下,两粒子同时从静止开始运动.已知两粒子同时经过一平行于正极板且与其相距 25 l的平面.若两粒子间相互作用力可忽略,不计重力,则M:m为( )
6+1=____
7+3=____
14-4=____
17-6=____
13+5=____