生活经验让我们已经熟知 ,自然界是由物质构成的 ,而物质的集合又组成了各种不同的物体 ,然而 ,不同的物体含有物质的多少一般不相同。例如 ,一扇铁门比一棵铁钉含有的铁多 ;一桶水比一杯水含有的水多。为了表示物体的这一性质 ,物理上引入了质量的概念 ,并且定义物体所含物质 Life experiences let us already know that nature is made up of matter, and that the collection of matter is made up of different kinds of objects. However, different objects contain generally different amounts of matter. For example, an iron door contains more iron than a nail; a bucket of water contains more water than a glass of water. In order to represent this property of an object, the concept of mass was physically introduced and the substance contained in the object was defined.