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Intro - Density - Pressure - Depth - Pascal - Archimedes - Continuity - Bernoulli - Solutions

Density

      Fluids are materials that can flow, and they include both gases and liquids. Air is the most common gas fluid and water is the most common liquid fluid. The density of a liquid or gas is one of the most important factors that determines its behavior as a fluid. Density is the mass per unit volume and is represented by the Greek letter rho (ρ).


ρ = mass / volume
The SI unit of density is kg/m3

      In chemistry we usually stated that at 4ºC the density of water was 1.0 g/mL. In physics we use the SI unit for density mentioned above. What is the density of water in the proper SI units?

      The density of blood is 1060 kg/m3. If a man's body weighs 690 N and contains about 5.2 x 10-3 m3 (5.5 qt) of blood, what percentage of the man's body weight is his blood?

      A convenient way to compare densities is to use the concept of specific gravity. The specific gravity of a substance is its density divided by the density of a standard reference material, usually chosen to be water at 4ºC. Being the ratio of two densities, specific gravity has no units.

s.g. = dens. of subs. / 1000 kg/m3

Substance
Density (kg/m3)
Solids
 
Aluminum
2700
Brass
8470
Concrete
2200
Copper
8890
Diamond
3520
Gold
19 300
Ice
917
Iron (steel)
7860
Lead
11 300
Quartz
2660
Silver
10 500
Wood (yellow pine)
550
Liquids
 
Blood (whole, 37 °C)
1060
Ethyl alcohol
806
Mercury
13 600
Oil (hydraulic)
800
Water (4 °C)
????
Gases
 
Air
1.29
Carbon dioxide
1.98
Helium
0.179
Hydrogen
0.0899
Nitrogen
1.25
Oxygen
1.43