The basic principle of paper-supported water

The atmospheric pressure 2113 exerts a greater force than water 5261, equivalent to that of a mercury vacuum pressure gauge; whereas when there is also gas in the cup 4102, the pressures of the gases on the left and right cancel each other out, and the paper cannot support the water, hence it cannot hold it up.

When conducting the paper-supported water experiment, the water cup should be filled to the brim, leaving no gaps. Otherwise, if gas enters, the atmospheric pressure will decrease, potentially leading to a failed experiment. If the water cup is turned upside down too slowly, water will flow out, resulting in a failed experiment. If the experiment is successful, the paper can support the water for about a minute, but if the paper strip remains wet for too long, it will eventually fall down.

The cause of atmospheric pressure

The pressure of a gas is caused by the frequent collisions of many molecular structures with the walls of the container. The collision of a single molecular structure with the wall of the container is very brief and its effect is not continuous. However, when many molecular structures frequently collide with the wall, the interaction force on the wall is continuous and uniform. The ratio of this working pressure to the total area of the wall is the measure of gas pressure.

After Torricelli measured the standard atmospheric pressure, everyone calculated the mass of gas above the entire area of the enterprise using the formula p=F/S. Then, by substituting the density of air, the volume was calculated, and by dividing it by the mass, the distance from the road surface to the top of the atmosphere could be determined.