Know how to calculate the force of density area
Mass = density × Volume, M= ρ 5. M is quality ρ V is density and V is volume. The mass of a substance per unit volume is called density. Use letters“ ρ” Expression
The calculation formula ofdensity is as follows ρ= m / V
Density unit: the international unit is kg / m3, the commonly used unit in the experiment is g / cm3, 1g / cm3 = 103kg / m3 
extended data:
Application
I. scientifically
1. Identify the materials that make up the object
density is one of the characteristics of matter. Each substance has a certain density, and the density of different substances is generally different. So we can use density to identify substances. The method is to measure the density of the material to be measured. By comparing the density measured with the density of various substances in the density table, we can identify what material the object is made of
2. Calculate the composition of various substances in the object
3. Calculate the mass of the object that is difficult to weigh or the volume of the object with complex shape
according to the variant form of density formula: M = v ρ Or V = m/ ρ， It can calculate the mass and volume of the object, especially some problems which are inconvenient to measure directly, such as calculating the volume of the irregular shape object, the mass of the monument and so on
Second, in agriculture, density is an important basis. It can be used to judge the soil fertility in agriculture. The soil with more humus is fertile, and its density is generally 2.3 × 10³ Kg / M;. When we select seeds, we can select seeds according to their sinking and floating in water: plump and robust seeds sink because of high density; Shriveled shells and other weed seeds float on the water e to their low density In instrial proction, such as the proction of starch using potatoes as raw materials, generally speaking, potatoes with more starch have higher density, so the yield of starch can be estimated by measuring the density of potatoes In instry, before casting metal, it is necessary to estimate how much metal to melt. The amount of metal required can be calculated according to the volume of the mold and the density of the metalsource: network density
From M = PV, P = m / V, M is mass, P is density, and volume is v
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for irregular, there are many calculation methods, because irregular shape means that volume V is not easy to measure, so we usually have some skills, such as dividing an irregular shape into several regular shapes for calculation, or putting some irregular insoluble figures into water for calculation.
density formula: ρ Density, mass and volume)
P = m / V
The algorithm for density is to divide the mass of an object by its volume
When the temperature and pressure change, the density of solid or liquid matter only changes a little. For example, near 0 ℃, the temperature coefficients of various metals (the change rate of the volume of the object when the temperature rises by 1 ℃) are mostly around 10-9. The pressure in deep water and underwater explosion can reach hundreds of atmospheres, or even higher (1 atmosphere = 101325 PA). In this case, the variation of density with pressure must be considered The density of human body is only 1.02 g / cm;, It's only a little more dense than water. The density of gasoline is less than that of water, so the oil stains you see on the road will float on the water. The density of sea water is greater than that of water, so it is easier for human body to float in the sea water
extended data
density is one of the characteristics of matter. Each substance has a certain density, and the density of different substances is generally different. So we can use density to identify substances. The method is to measure the density of the material to be measured. By comparing the density measured with the density of various substances in the density table, we can identify what material the object is made of
it can be used to judge the fertility of soil in agriculture. The soil with more humus is fertile, and its density is generally 2.3 × 10³ Kg / M;. When we select seeds, we can select seeds according to their sinking and floating in water: plump and robust seeds sink because of high density; Shriveled shells and other weed seeds float on the water e to their low density
first calculate the volume, 500 × five hundred × 10 = 2500000 cubic mm
and then according to ρ= M / V,
its mass m = 2500000 cubic mm × 1.2 kg / m3 = 0.003 kg
the mass of this object is 0.003 kg