不把嘴唇放到水里，你能把杯子里的水喝进肚子里去吗?能!把杯子凑到嘴边，然后用力地去吸，吸的时候，胸部扩大，肺和嘴里气体压强减小，嘴附近的空气就会向嘴里跑，离嘴越近的地方，水面上方空气流动得越快，空气对水面的压强也就越小；离嘴越远的地方，水面上方的空气流动得越慢，气压也就越大，在空气压力作用下，靠近嘴的水 Don’t put your lips into the water. Can you drink the water from the cup? Can you put the cup to your mouth and suck hard? When you suck, your chest expands, and your lungs and mouth have a gas pressure. To reduce, the air near the mouth will run in the mouth. The closer to the mouth, the faster the air flows above the water surface, the smaller the air pressure will be on the water surface; the farther away from the mouth, the air above the water surface. The slower the flow, the greater the pressure, the water near the mouth under the pressure of the air