Body weight is usually determined experimentally. For this purpose take cargo, put it on scales and receive result of measurement. But at the solution of the physical tasks given in textbooks, measurement of weight for the objective reasons is impossible, but there are any given data on a body. Knowing these data, it is possible to determine body weight indirectly by calculation.
Instruction
1. In school courses of physics, chemistry, astronomy it is possible to meet a concept of weight. On body weight find reciprocal values - the volume, density, force. Weight - a quantitative index of substance therefore in tasks in chemistry the amount of substance is found, proceeding from weight. Weight depends on properties of substance of which the body and also from amount of this substance consists. There are several main methods of calculation of weight. Choose them depending on what other physical quantities are set in a task. Let's consider each case separately.
2. The most widespread way of finding of body weight is its calculation on the basis of the volume and density. However, in a number of tasks before determination of weight it is necessary to count volume, being guided by other geometrical characteristics of a body. For example, for a cylinder with known for the area of the basis and height made of substance with the known density, weight will be equal: m=?*V=?*S*h, where Vtsil.=S*h? - density, S is the area of the basis of a cylinder, h is cylinder height. If volume is specified in a task directly, for finding of weight it is rather simple to increase it by density: m=?*V
3. Other section of physics where it is necessary to count weight - dynamics. Usually in it interaction between bodies, action of external forces on bodies, a condition of bodies at uniform motion is studied. Any body by force of F receives acceleration in interaction with other body. At the same time, it some mass of m. Masses it is connected with force the following ratio: F=m*a where an is acceleration of the set body; m - the mass of a telaotsyud it is possible to learn body weight: m=F/a
4. In chemistry we occur in textbooks concepts of amount of substance and molar weight. Through these two sizes it is also possible to express the mass of substance. As the amount of substance is the physical quantity proportional to number of particles of which substance, and molar weight - weight of one mole of a substance consists, it is possible to calculate the mass of the set amount of this substance as follows: mv =mv*nv, where MV - molar weight, nv - amount of substance