frictional force短语¹¹⁴⁴⁶⁷⁺⁴ 基本例句 摩擦力 According to characters of geometrical shape and frictional force of steel ball, the practical mechanism with special function is designed by using steel ball composed of special construction. 利用钢球的几何形状及在滚动中的低摩擦特性，将其与一些经专门设计的构件组合，可以构成功能独特的实用机构。 cnki