pressure - the value of physics, which shows the numerical value of the ratio of the force acting on the unit adopted specific surface.It is assumed that the direction of this force exactly perpendicular to the surface area.If the SI system, which was adopted on the open spaces of the CIS countries, the strength of matter Newton or kilogram-force, and the area - square centimeters (millimeters, meters), we get:
P = F / S = N / cm2 = Pa
Pascal - is one of the varieties of values (used in engineering and physics).Generally, the values are indicated in MPa - megapascals.This is useful for reducing the number of zeros.In the art and life often use the term "atmosphere".Absolute pressure as well as the relative, can be measured in the "atmospheres" Pa, and other units.
In practice, the term "atmosphere" also has a few concepts and technical standard.Standard, physical or normal atmosphere is marked by "bar" (ATA) and the default value - 101,325 Pa, which means that the pressure of mercury at sea level and at a temperature of 0 degrees Celsius.You can also find expression 760 mm.rt.s.(mmHg).Technical atmosphere has nothing to do with the term absolute pressure as it has a different definition and unit "AT" (ATI).The definition states: "the force acting perpendicularly on the weight (1 kg) with the gravitational acceleration (1g) uniformly per unit area (1 cm2)."
There are also certain:
absolute pressure - the pressure measured relative to absolute zero - vacuum (ata).
Relative pressure - pressure measured relative to standard atmosphere (atm).
overpressure - can either be a relative, and to be his difference (ATI).
Very often, the concept of absolute and gauge pressure isolated as the only two types.In fact, no significant difference in relative excess pressure and no.It's more turns of speech that are more accustomed to using professionals of an industry.
Let's go back to the notion of absolute pressure.As already mentioned, it is an absolute indicator, ie,measured from the physical zero.It's like a scale on the line - you measures the 0 and how much you need.In nature, this concept is rarely used in the calculations, since "overboard" always already there is some pressure.Therefore, it is more convenient to measure him.For example, the pressure in the tires of your car to the service station master tells you in the atmosphere (for passenger about 2.2 atm).Cylinders are also the unit of measure - the atmosphere, but technical.This is due to the fact that when using essential difference.
special note is that the air pressure with height naturally changes.Changing pressure absolute and relative conditional with every kilometer.To define it, should take into account all the external factors: temperature, density and gravitational acceleration.These data are standardized for each height.They are tabulated pressure distribution along the height or may be presented as graphs.This information is useful primarily to designers of aircraft (LA).Since the aircraft has a range of working heights from 0 to 12 km (passenger).And, then, all systems, machines and working aircraft engines should be designed taking into account different environmental conditions.
in the world use a variety of value that is measured as the excess, and the absolute pressure.It all depends on the geographical region and area of use.Below the main chain of pressure units:
1 Pa = 9.87 * 10-6 atm.= 1.02 atm.= 1.02 kg / cm2 = 10-5 bar = 1,45 * 10-4 PSI =
= 7,5 * 10-3 torr= 0.120 mm.vod.st
As you can see, the range of pressure units is quite large.From this list, in the CIS countries the most frequent Pa, atm., Al., Kg / cm2, mmHg
Among other things, in the nature and processes meet the static and total pressure.Static pressure - the pressure, which is measured by the flow of the working fluid (ie, its natural pressure).The total pressure (pressure on the locked parameters) - is the pressure measured directly in the stream (i.e. during braking before the flow sensor).
pressure affects man to a greater extent than the temperature, since the temperature of human body has some margin, and pressure - is very small.That is why the elderly and sick people are very sensitive to changes in pressure.For technical purposes using pressure measuring instruments - pressure gauges for hydrometeorological - barometers.
