The majority of bodies has complex structure, they consist of various substances. Therefore it is almost impossible to find their density by means of tables. To get an idea of their structure, use such concept as average density which pays off after measurement of weight and volume of a body.
It is required to you
- - scales;
- - measured cylinder;
- - table of density of various substances.
Instruction
1. If the body consists not of uniform substance, find its weight by means of scales, and then measure volume. If it is liquid, perform measurement by means of a measured cylinder. If this solid body of the correct form (cube, a prism, a polyhedron, a sphere, a cylinder, etc.), find its volume geometrical methods. If a body of irregular shape, ship it in water which is filled in in a measured cylinder, and determine body volume by its rise. Divide the measured body weight into its volume, as a result receive the average density of a body ρ=m/V. If weight was measured in kilograms, express volume in m³ if in grams – in cm³. Respectively density will turn out in kg/m³ or g/cm³.
2. If it is not possible to weigh a body, learn density of materials of which it consists, then measure the volume of each component of a body. Then find the mass of materials of which the body consists, having multiplied their density on volumes and total amount of a body, having put volumes of its components, including emptiness. Divide body lump into its volume, and receive the average density of a body ρ = (ρ1•V1 + ρ2•V2+ …) / (V1+V2+ …).
3. If the body can be shipped in water, find its weight in water by means of a dynamometer. Determine the volume of the pushed-out water which will be equal to the volume of the body shipped in it. When calculating consider that density of water is 1000 kg/m³. To find the average density of the body shipped in water to its weight in Newtons, add the work of number 1000 (water density) on the acceleration of gravity of 9.81 m/s² and body volume in m³. Divide the turned-out number into the work of volume of a body and 9.81 ρ= (R + ρv·V·9.81) / (9.81 • V).
4. When the body floats in water, find the volume of the pushed-out liquid, body volume. Then the average density of a body will be equal to the relation of the work of density of water on its volume which is pushed out by a body and the volume of the body ρ = ρv·Vv/Vt.