初中物理P184对有用功,额外功和总功的定义如下: 利用机械工作的时候,对我们有用的功叫有用功,这部分功是必须做的。 对人们没有用但不得不额外做的功叫额外功。 有用功与额外功的和叫总功。 这三个概念的定义都属于描述性的,乍看起来通俗易懂,但更进一步对概念中的几个关键词,“有用”、“没有用”、“必须”、“不得不”进行探究,发现这些关键 Junior high school physics P184 defines useful work, extra work and total work as follows: When working with machinery, useful work for us is called useful work. This part of work must be done. The work that is not useful to people but has to be done extra is called extra work. The sum of useful work and extra work is called total work. The definitions of these three concepts are descriptive and seem simple and straightforward, but they further explore the keywords in the concept: “useful,” “not useful,” “must,” and “have to”. , find these key