![]() ![]() A common example is sand: if gently filled into a container, the density will be low when the same sand is compacted into the same container, it will occupy less volume and consequently exhibit a greater density. The density of a solid material can be ambiguous, depending on exactly how its volume is defined, and this may cause confusion in measurement. Another instrument used to determine the density of a liquid or a gas is the digital density meter - based on the oscillating U-tube principle. A common laboratory device for measuring fluid density is a pycnometer a related device for measuring the absolute density of a solid is a gas pycnometer. Where the integration is over the volume of the body V.Ī very common instrument for the direct measurement of the density of a liquid is the hydrometer, which measures the volume displaced by an object of known mass. ![]() The mass of the body then can be expressed as If the body is not homogeneous or heterogeneous, the density is a function of the coordinates, where is elementary volume with coordinates. Hydrostatic weighing is a method that combines these two. The mass is normally measured with an appropriate scale or balance the volume may be measured directly (from the geometry of the object) or by the displacement of a fluid. Some scholars have doubted the accuracy of this tale, saying among other things that the method would have required precise measurements that would have been difficult to make at the time.įor a homogeneous object, the mass divided by the volume gives the density. This story first appeared in written form in Vitruvius' books of architecture, two centuries after it supposedly took place. As a result, the term "eureka" entered common parlance and is used today to indicate a moment of enlightenment. Allegedly, upon this discovery, he went running naked through the streets shouting, "Eureka! Eureka!" (Greek "I found it"). ![]() Īrchimedes knew that the irregularly shaped wreath could be crushed into a cube whose volume could be calculated easily and compared with the weight but the king did not approve of this.īaffled, Archimedes took a relaxing immersion bath and observed from the rise of the warm water upon entering that he could calculate the volume of the gold crown through the displacement of the water. In a well-known story, Archimedes was given the task of determining whether King Hiero's goldsmith was embezzling gold during the manufacture of a wreath dedicated to the gods and replacing it with another, cheaper alloy. In some cases density is expressed as the dimensionless quantities specific gravity (SG) or relative density (RD), in which case it is expressed in multiples of the density of some other standard material, usually water or air/gas. (rho) is the density, is the mass, is the volume.ĭifferent materials usually have different densities, so density is an important concept regarding buoyancy, metal purity and packaging. ![]()
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