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初中物理第一册131页,在叙述离心式水泵的工作原理中,讲到泵壳里灌满水后,叶轮在动力机带动下旋转,泵壳里的水也跟着旋转,同时被叶轮甩入出水管,水被甩出时,叶轮附近的压强就减小,比大气压小得多。因此……。 同学们对叶轮附近的压强为什么会减小,就很难理解,为突破这一难点,可增做这样一个实验: 器材:漏斗、乒乓球各一个。 步骤:1.右手握住漏斗颈,斗口向下,左手托住乒乓球,使其位于漏斗口内。 2.用嘴向漏斗颈里吹气,左手脱离乒乓球。 现象:乒乓球并不下落(如图1)而是紧紧地吸附
On the 131st page of the junior high school physics book, in describing the working principle of the centrifugal water pump, when the pump shell is filled with water, the impeller rotates under the power machine, the water in the pump casing also rotates, and the impeller is thrown into the outlet pipe. When the water is thrown out, the pressure near the impeller decreases and is much smaller than the atmospheric pressure. therefore……. It is difficult for students to understand why the pressure near the impeller will be reduced. In order to overcome this difficulty, we can add such an experiment: Equipment: one for the funnel and one for table tennis. Steps: 1. Hold the funnel neck with your right hand and lower your mouth down. Hold the table tennis ball with your left hand so that it is inside the funnel mouth. 2. Blow into the neck of the funnel with your mouth and leave your left hand from the table tennis ball. Phenomenon: Table tennis does not fall (Figure 1) but is tightly adsorbed