论文部分内容阅读
水向高处流“水往低处流”。这是大家熟知的俗语。可是,当你为了消灭蚊子、苍蝇而使用喷雾器的时候,却会看到一种反常的现象:在插入药水的竖管中,液体破例地由下而上倒流(图1)。这是什么道理呢?原来这是力学中的伯努利原理的一种现象。那么,伯努利原理是怎样的呢?在一定条件下,水流或气流的静压力是同速度有关系的。粗略地说,如果速度小,则静压力就大;速度大,静压力就小。这一原理,是力学家丹尼尔·伯努利于1726年首先提出来的,所以就叫作伯努利原理。可是,喷雾器中,插入药水的
Water flows high and “water flows down.” This is a familiar saying. However, when you use a sprayer in order to eliminate mosquitoes and flies, you will see an anomalous phenomenon: In the vertical pipe into which the medicine is inserted, the liquid reverses from the bottom up (Figure 1). What is the reason for this? It turns out that this is a phenomenon of the Bernoulli principle in mechanics. So, what is Bernoulli’s principle? Under certain conditions, the static pressure of water flow or air flow is related to speed. Roughly speaking, if the speed is small, the static pressure is large; the speed is large and the static pressure is small. This principle was first proposed by mechanic Bernard Daniel Bernoulli in 1726, so it is called Bernoulli’s principle. However, in the sprayer, insert the syrup