The weight and volume can be connected by other physical quantity which is used when calculating both above-stated parameters, - weight. But in one actions of it not to make therefore it is necessary to consider formulas of calculation and volume and weight of this body.
Instruction
1. The formula of calculation of body weight has an appearance: P=m*g where P-body weight, m is body weight, g is acceleration of gravity. There is no volume in this formula, so it should be connected with the sizes specified in a formula, for example, by weight. It is impossible to remove the acceleration of gravity as it – the constant size equal of 9.8 N/kg (Newton divided into kilogram). The volume and body weight are united by other physical formula: V = m / ρ where m is weight, V – body volume, ρ – the substance density, a constant table value for concrete substances. Write down it in a look, convenient for work: m = V*ρ
2. Substitute a weight formula (m = to V*ρ) in a formula of the body weight (P=m*g), the new formula for calculation of weight of the specified body will turn out: P=V*ρ*g. Here also the settlement formula of body weight through its volume turned out. In it the acceleration of gravity, g, and density, ρ, are constants (density only for this body). The direct dependence between the volume and body weight became visible. The more body volume, the more its weight.
3. Example of the solution of a task. Find the weight of a glass sphere of 0.2 м^3 (cubic meter). Decision. In this condition there are three known sizes: volume (V=0.2 м^3), the acceleration of gravity (9.8 N/kg) and density which is determined in the table by substance of which the body consists, (density flew down ρ = 2500 kg / м^3). P=V*ρ*g = 0.2 м^3*2500 kg / ¼^3*9.8 N/kg = 4900 N. During the work with units of measure: reduce cubic meters and kilograms, there are newtons – force unit of measure. Body weight is force therefore it is measured in newtons.