Pressure around
Air pressure (atmospheric pressure) in any unit area on the surface of the air pressure generated by molecular motion. Is usually measured by a high degree of cross-sectional area of units at and above the weight of the vertical atmospheric column
(1) the definition of gas pressure
Role in vessel wall of gas pressure on the unit area is the gas pressure.
p=F/S p = F / S
(2) gas pressure causes
From the molecular kinetic theory we can see that the gas pressure is frequently a large number of molecular collisions arising from the container wall. A single molecule of the vessel wall collision time is very short role is not continuous, but a large number of molecular collision frequency wall, right wall of the force is a continuous, uniform, this pressure and the ratio of wall area is the pressure of the size of .
(3) The unit of pressure
International System unit: Pascal, abbreviated Pa symbol Pa.
Common unit: standard atmosphere.
1atm=1.013×10^5Pa=760mmHg 1atm = 1.013 × 10 ^ 5Pa = 760mmHg
(4) The method of calculating pressure
Equilibrium conditions are usually law and Newton’s laws of motion method (the formula is only a rough calculation, and sometimes the values measured are not allowed, all should be based on the actual date).
The size of air pressure and altitude, air temperature, atmospheric density, is generally higher with a high degree of exponential decline. Pressure with diurnal and annual variation. One year, the high pressure in winter than in summer. One day, the pressure has a maximum value, a minimum value, respectively, in 9 to 10 am and 15 ~ 16 o’clock, there is a second high-value and a second low-value, respectively, in 21 to 22 am and 3 ~ 4 pm . Diurnal variation of atmospheric pressure to a lesser extent, generally 0.1 to 0.4 kPa, and decreases with higher latitude. Pressure changes and wind, the weather is good or bad and so close, so it is important to meteorological factors. Commonly used pressure units Pa (Pa), mm Hg higher (mm · Hg), millibar (mb). The conversion relationship between them as follows: 100 Pa = 1 mbar ≈ 3 / 4 mm Hg higher. Commonly used in meteorological observation instrument measuring atmospheric pressure with mercury barometer, air box barometer, barometer. 101.325 kPa pressure (760 milli-Migon column), known as the standard atmospheric pressure, which is equivalent to the acceleration of gravity is 9.80665 meters / sec 2, the temperature is at 0 ℃ 760 millimeters of mercury column vertical high pressure, standard atmospheric pressure, first from Italy Scientists measured Tory split profits.
Related words:
Barometer: Measuring air pressure equipment, the most common are mercury barometer and the two kinds of empty boxes barometer. Several instruments are more accurate …