Principle of compressed air
Air occupies a certain amount of space, but it does not have a fixed shape and volume. When pressure is applied to the air in the closed container, the volume of the air is compressed to increase the internal pressure. When the external force is removed, the air will return to its original volume under the action of internal pressure. If there is an object that can move in the container, when the air returns to its original volume, the object will be pushed outward by the pressure of the air inside the container. This principle is widely used in production and life. For example, the compressed air is blown into the ball. The more the gas is, the harder the ball is; the compressed air is blown into the tire, and the tire can withstand a certain weight. In large cars, compressed air is used to switch the doors and brakes; the hydraulic press uses compressed air to pressurize the water. In the factory, compressed air is used to start the hammer and iron; in the coal mine, it can start the wind and drill. It is also used to pipe liquids and granular objects.