1　课后实验及其存在问题图 1“借助铅笔或木棍把气球塞进一个瓶子里 ,并把气球口拉大反套在瓶口上 .用力向气球里吹气 ,你会发现 ,无论怎样用力去吹 ,都不能把瓶内的气球吹大 .做这个实验观察现象并解释其原因 .”(如图 1 ) .这是中等师范学校教科书 (试用本 )《物理》第一册 1 After-school experiment and its problems Figure 1 “Use a pencil or wooden stick to stuff the balloon into a bottle and put the balloon on the back of the bottle. Blow it into the balloon and you will find that no matter how hard you use it, If you blow it, you can’t blow up the balloons in the bottle. Do this experimental observation and explain the reasons.” (Figure 1) This is the textbook for secondary normal schools (trial version).