将气球吹大后，用手捏住吹口，然后突然放手，气球内气流喷出，气球因反冲而

将气球吹大后，用手捏住吹口，然后突然放手，气球内气流喷出，气球因反冲而运动。可以看见气球运动的路线曲折多变。这有两个原因：一是吹大的气球各处厚薄不均匀，张力不均匀，使气球放气时各处收缩不均匀而摆动，从而运动方向不断变化；二是气球在收缩过程中形状不断变化，因而在运动过程中气球表面处的气流速度也在不断变化，根据流体力学原理，流速大，压强小，所以气球表面处受空气的压力也在不断变化，气球因此而摆动，从而运动方向就不断变化。

After blowing up the balloon, hold the mouthpiece with your hand, and then suddenly let go. The air flow in the balloon is ejected, and the balloon moves due to recoil. It can be seen that the route of balloon movement is tortuous and changeable. There are two reasons for this: first, the thickness and tension of the blown balloon are uneven, which makes the balloon contract unevenly and swing when deflating, so that the moving direction changes constantly; Second, the shape of the balloon changes constantly in the process of contraction, so the air velocity at the surface of the balloon is also changing in the process of movement. According to the principle of hydrodynamics, the flow velocity is large and the pressure is small, so the pressure of the air on the surface of the balloon is also changing. Therefore, the balloon swings, so the direction of movement is constantly changing.

After the balloon is blown up, hold the mouthpiece with your hand, and then suddenly let go, the air flow in the balloon spurts out, and the balloon moves due to recoil. You can see that the route of balloon movement is tortuous and changeable. There are two reasons for this: First, the inflated balloons are uneven in thickness and tension, which makes the balloons contract unevenly and swing when deflated, so that the movement direction is constantly changing; Second, the shape of the balloon is constantly changing during the contraction process, so the air velocity at the balloon surface is also constantly changing during the movement process. According to the principle of fluid mechanics, the velocity is high and the pressure is low, so the pressure of the air on the balloon surface is also constantly changing, so the balloon swings and the movement direction is constantly changing.