在一部电影中有这样一组镜头:解放前,一米店老板,他每年向农民收购粮食时,明明是100斤的粮,可用他的大秤一称,却只有80斤了.同是一杆秤,而当他把粮卖给穷人时,明明只有80斤,到了他这杆罪恶的大秤上一称,竟比100斤还多.当时,人们都很气愤,一致要求换秤称,而这位老板却说什么也不肯,还假仁假意地解释道:“我买进卖出都是用同一杆秤,我卖粮给你们时,秤尾总是翘得高高的,我买你们的粮时,秤尾总是压得低低的,这难道还对不起大家吗?”就在这时,一个小伙子气愤不过,一把抢过老板手中的杆秤,猛地往膝盖上一磕,只听“喀嚓”一声,秤杆断成两节,一个奇怪的现象出现了:从秤杆中流出了一大滩水银!原来他的秤杆是空的,里面注了水银.同学们,你们知道这空心水银秤为什么 In a movie there is such a set of shots: before the liberation, one meter shop owner, every year when he acquired grain from the peasants, it was obviously 100 pounds of grain, available to his weighing scale, but only 80 pounds. A bar scale, and when he sold the grain to the poor, it was clear that only 80 pounds went to him on this evil scale, which was more than 100 pounds. At that time, people were very angry and agreed to change the scales, But the boss said nothing, but also Honesty deliberately explained: “I buy and sell are the same scale, I sell food to you, the scales tail is always high, I bought Your grain, the tail is always depressed, Is it still sorry you? ”At this time, a young man angry, but grabbed the boss’s hand scale, suddenly a knock on his knees , Just listen to “click” sound, the beam broken into two sections, a strange phenomenon appeared: outflow from the beam of a large bank of mercury! He had the beam is empty, which filled with mercury. Classmates, you Know why this hollow mercury scale