What determines the pressure in the liquid and gas?

As already mentioned, the pressure is literally surrounding us. It exists in any object or organism. Suffice it to say that a pressure of 100 kN / m2 is applied to any object or living creature on the surface of the Earth. This is the pressure of the air column. People somehow perceive the visual picture of pressure as directed forces in a closed volume. This is true for isolated vessels. In open containers, this picture is a consequence of the pressure of the column. Any pressure in the liquid and gas is the result of the "behavior" of the molecules of the material itself. It is absolutely true for a liquid, a gas, and a solid body that pressure as a physical quantity is the total force of impacts of all molecules on the surface.

From the course of elementary physics it is known that the formula for the pressure of a liquid and a gas has the form:

P = ρ × g × h, [Pa]

Consider where such components are. If you take any volume of liquid / gas, then determine its pressure on the area can be as follows. Pressure is the force applied to the area - F / S. This is understandable to any student. Now we will write down what is the force of the second law of Newton - the mass of the body, multiplied by the acceleration (in this case - when the working body in a state of calm - acceleration of gravity). In turn, the mass is the product of density per volume occupied by the body. And the volume can be decomposed as the product of the area to the height. In the form we obtain:

P = F / S = (m × g) / S = (V × ρ × g) / S = (S × h × ρ × g) / S = ρ × g × h

Where P is the pressure, F is the force, S is the distance, m is the mass, g is the acceleration due to gravity, V is the volume, ρ is the density, h is the height

Pa = N / m2 = (kg × m / s2) / m2 = (m3 × kg / m3 × m / s2) / m2 = (m2 × m × kg / m3 × m / s2) / m2 = m × kg / M3 × m / s2 = kg / (m × s2)

The units shown show how Pascal is formed. Blaise Pascal was a famous scientist, including in the field of physics. He is the author of the fundamental law, which answers the question: "How to find the pressure of a gas or liquid if it is at rest?" On the basis of his experience, one of the basic laws of physics and hydraulics was obtained-the pressure from the body (liquid or gas) at any chosen point equally over the entire surface with which the body interacts.

More modern science - hydraulics is also armed with the law with its authorship - "The law of constancy of pressure". It says that the liquid head will be constant at any point of the liquid, provided it is at rest. These foundations and laid the foundation for the calculation of complex systems now and allowed to create unusual technical solutions. Nowadays, any system or mechanism working with a liquid or gas is compulsorily calculated for not exceeding the maximum permissible values (which are known from experiments for different materials) that form the pressure in a liquid and gas.

If we consider the pressure when the liquid is at rest, then we should speak of hydrostatic pressure. If we are talking about the dynamics, then it is more urgent to talk about the hydro-impact. Hydro-impact is a phenomenon that occurs in tanks and pipes, due to a sharp increase in pressure in any place. All hydromechanisms and their elements are calculated to the ultimate static pressures and short-term casts - hammers. For example, the frequent cause of the failure of water faucets is a hydro shock. A big jump on the main line can reach the crane, and it will fail (in whole or in part).

It is curious that even though liquid and incompressible (practically), on the one hand this improves the transfer of momentum. On the other hand, if the path is long and there is interference (for example, a domestic filter), the hydrostatic shock can completely go to waste. The pressure in the liquid and gas can also be changed by other factors. The first thing that comes from the formula is the change in the height of the container. This principle was actively used in ancient times by various civilizations, and also can be visually seen in the villages. Still remaining from the time of the USSR water towers work on this principle. In a large capacity under the pressure of the discharge pump, water is supplied to a certain level. This is automatically regulated by the float, as in the drain tank of your toilet bowl (when the level reaches the float it floats up and the lever closes the water supply). Next, the liquid flows self-propelled, because Its level above the ground is large, and the hole is small.

In addition, the pressure can be changed by changing the temperature. The speed of movement of molecules depends on it, and hence the number of strokes. It would seem that the larger it is, the higher the pressure in the liquid and gas. But is it? Not really. It's about properties. Water, for example, freezes and increases in volume, and air - decreases. A simple example - who owns dachas, knows that for the winter it is necessary to drain the water from the system of the main, so that pipes and taps do not break. Another example about the air - inflate the balloon and place it in the refrigerator for 10 ... 15 minutes. When you pull it out, it will decrease in volume. If you pour it with hot water from the kettle, it will swell quickly.

Pressure is a phenomenon with which we have to not only live, but also reckon. Remember diving for depth or a sound wave with a strong thunder. Be always careful and remember that pressure is the movement of molecules, and molecules are small particles of life!