Space of Three Dimensions: Solids
المؤلف:
GEORGE A. HOADLEY
المصدر:
Essentials of Physics
الجزء والصفحة:
p-31
2025-10-21
41
A volume has three dimensions, length, breadth, and thickness. The unit of volume is a cube with the unit of length for each edge. In the metric system it is the cubic centimeter (c.c. or cm.3), and the scale of the table is 1000.
Units of Mass and Weight. - The French standard mаss is the kilogram (kg.). This is the mass of a cubic decimeter of pure water at 4° C. The gram (g.), equal to one thousandth of the kilogram, is the practical unit in physics. Decimal subdivisions and multiples of the gram are named by using the same prefixes as with the meter. The standard pound in this country is derived from the International Prototype Kilogram. The exact relation is, 1 lb.= 0.4535924277 kg.; but for ordinary purposes the following are used as equivalents:
Since at any one place the weights of bodies are directly proportional to their masses, and since the variation in weight with location on the earth's surface is not very great, the terms that are applied to masses (gram, pound, ounce, etc.) are commonly applied to the corresponding weights also.
It is often important in physics to compare the masses of equal volumes of different substances, or the volumes of equal masses. By the density of a body is meant the ratio of its mass to its volume, or the mass of a unit volume.
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