If you look at the electrical force, the force of electricity, proton and electron or something, it's not proportional to the mass of either object.

如果你考察电作用力,即电现象产生的力,质子啊,电子啊,或者其它什么东西,这种力不和物体的质量成比例

耶鲁公开课 - 基础物理课程节选