活动1:基于现象,了解浮力(教师播放视频《中国航母“辽宁号”》《“死海”畅游》)师:巨大的钢铁航母为什么可以浮在海面上?人为什么能浮在“死海”水面上?生:“航母”和“人”都受到水向上的托力,这种力叫做浮力。(教师出示系有细线的氢气球,放手后飘向空中,如图1) Activity 1: Based on the phenomenon, understand buoyancy (teachers play the video “China’s aircraft carrier ” “Liaoning ” “” Dead Sea“ swim ”) Division: Why can a huge steel aircraft carrier float on the sea? Why can people float in “Dead Sea” on the surface of the water: “Aircraft carrier” and “Human” are all subject to water upward force, this force is called buoyancy. (The teacher shows a balloon with a thin line of air. After letting go, it floats into the air, as shown in Figure 1)