Any substance, including, and liquid, has two characteristics: specific weight and density. Having measured or having calculated these parameters, it is possible to draw a conclusion on a number of other properties of substance. It is possible to carry out such measurement or calculation in various ways.
Instruction
1. Quite often specific weight is confused with density, however, these terms have various value. Specific weight is not physical and chemical characteristic of substance as at its definition there is an acceleration of gravity of g=9.8 м/с^2. In other words, specific weight differs from density in the same, than weight differs from weight. Density is called the relation of mass of substance to its volume, and specific weight - the body weight relation to its volume: γ=mg/V. As density represents the weight relation to volume, write down a formula for finding of specific weight in the following look: γ=ρg.
2. If necessary find specific weight by calculations through the weight and volume, or an experimental way, comparing values of pressure. On the basis of the equation of a hydrostatics find value of this size as follows: P=Po+γh. This method is applied when all three measured sizes are known: P, Po, h. The formula for finding of specific weight in that case takes the following form: γ=P-Po/h. This equation is widely applied to the description of action of communicating vessels. From experimental data it is possible to draw a conclusion that at each substance in communicating vessels the height and the speed of spreading on vessel walls will turn out. Knowing them, it is possible to calculate the specific weight of liquid.
3. The Archimedes force formula is also applied to calculation of specific weight. It is known that Archimedes force is the pushing-out force. Imagine that cargo of some mass of m which floats on a water surface is given. It is affected by two forces, one of which - gravity, and the second - the Archimedes force which pushes out this body in the direction, the return to mg vector. The formula of Archimedes force has the following appearance: Fapx.=ρgV. As the work ρg to equally specific weight of liquid, write down this equation in the following look: Fapx.=γV. Now express from this equation a variable γ as follows: γ=Fарх. / V.