In ordinary life of word meaning "weight" and "weight" coincide – for example, it is said that the subject weighs 10 kilograms. However in science these concepts are various. Body weight is the physical quantity characterizing properties of a body directly proportional to the volume and density. Unit of measure - kilogram. Its size is invariable both on Earth, and in zero gravity. Body weight is directly proportional to the body weight and acceleration. Air, as well as any other substance, has weight.
It is required to you
- - air volume;
- - air density;
- - aneroid barometer;
- - thermometer;
- - manometer.
Instruction
1. There is a concept of the International standard atmosphere. The air having the barometric pressure of 760 mm Hg., temperature +15 gr is taken for a zero reference point. With, density is 1.225 kg/m3. Body weight is calculated on a formula: m=Vρ, where V – the volume of substance, m3; ρ – density of substance, kg/m3. Density of air accept 1.225 kg/m3. Knowing air volume, find its weight.
2. Body weight is described by a formula: G=mc where G is body weight, is measured in Newtons; m – body weight, kg; with – acceleration, m / с2. If in a condition air does not move and is in terrestrial conditions, acceleration is equal to acceleration of gravity: G=mg. Substitute value of mass of air in a formula and find its weight.
3. If temperature and density of air differs from taken for the standard, mass of the set volume of dry air calculate from ideal gas law of Mendeleyev - Clapeyron where M – the molar mass of gas (for air it is equal to 29*10-3 kg/mol); R – universal gas constant. R=8.314472 m2kg with-2 Mol-1 K-1; T – gas temperature, To; p - absolute pressure, Pa.
4. For calculation it is required to know pressure and air temperature. Measure pressure by means of the aneroid barometer, temperature – the thermometer. Transfer temperature from degrees Celsius to Kelvins, having added to value of temperature 273. Translate pressure from mm Hg. in pascals, 1 mm Hg. =133.3 Pas. If air is put into a vessel and is under pressure, measure excessive pressure by the manometer. Put sizes of excess and atmospheric pressure, and you receive value of absolute pressure: r=ratm +rizb.
5. Having substituted the found sizes in Mendeleyev-Clapeyron's equation, solve it and find the mass of air for the set air volume. Knowing weight, calculate air weight by a formula from a step 2.