编者：简单机械一章知识在生产、日常生活中用途极大，为了学好这一章，几位老师总结了多年的教学经验，通过归类、方法指导，及生活中的趣事、小制作、小实验等，帮助同学们提高学习兴趣．希望同学们多动眼看、动脑想、动手做，使这一章知识出会贯通。在《简单机械》这章书中? Editor: The simple machine chapter is very useful in production and daily life. In order to learn this chapter, several teachers have summarized the teaching experience of many years, through classification, method guidance, and interesting things in life, small production, and small Experiments, etc., to help students improve their interest in learning. I hope that the students will look, think, and do something to make this chapter knowledgeable. In the chapter “Simple Machinery”?