Atmospheric pressure is defined by presence of body weight at air which makes the atmosphere of Earth. This atmosphere presses on its surface and objects which are on it. At the same time on the medium-sized person presses the cargo equivalent to 15 tons! But as the air which is in an organism presses with the same force, we do not feel this loading.
It is required to you
- Mercury barometer, aneroid barometer, ruler
Instruction
1. Atmospheric pressure it is measured barometer. It is possible to carry a mercury barometer to the simplest and effective devices. It represents the vessel filled with mercury and the tube 1 m long soldered on the one hand. Fill a tube with mercury, and lower in a vessel in which there has to be a number of this substance too. After that mercury will fall a little. Carefully measure mercury column height over liquid level in a vessel. Pressure of this column of mercury will be to equally atmospheric pressure. Atmospheric pressure of 760 mm of a mercury column is considered normal.
2. To transfer pressure to mm of a mercury column in Pascals which are accepted in the international system of calculation use coefficient 133.3. Just increase by this number value of atmospheric pressure in mm of a mercury column.
3. Other way of measurement of atmospheric pressure – by means of the aneroid barometer. In it there is a metal box with corrugated walls that will increase the air area of contact with its surface. From it air is pumped out therefore it is pressed at increase in atmospheric pressure and again finishes at its reduction. This metal box, actually, is also called the aneroid. The mechanism transferring its movement to an arrow with a scale which is graduated in mm of a mercury column and kilopascals is attached to it. Atmospheric pressure in each timepoint in this point of space is also determined by it. The fact that atmospheric pressure changes with change of height of the observer above sea level is known. For example, in the deep mine it increases, and on the high mountain – decreases.
4. If atmospheric pressure at sea level is known, then its change can be calculated. For this purpose to the exhibitor build (number 2.72) in degree for which calculation multiply numbers 0.029 and 9.81, increase result by height of rise or lowering of a body. Divide the turned-out value into number 8.31 and air temperature in Kelvins. Before an exponent put the sign "minus". To the exhibitor, the received degree built in, increase by value of pressure at sea level of P=P0•e^ (-0,029•9,81 • h/8.31•T).