题目

．两个分别带有电荷量和+的相同金属小球（均可视为点电荷），固定在相距为的两处，它们间库仑力的大小为。两小球相互接触后将其固定距离变为2r，则两球间库仑力的大小为（       ）A．       B．        C．       D．  答案：A 解析:略 It has been proved________violence on television has a bad effect on the development of children. [     ]A．whether  B．because  C．when  D．that