Specific weight

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The specific weight, also known as the unit weight (symbol Template:Mvar, the Greek letter gamma), is a volume-specific quantity defined as the weight W divided by the volume V of a material: γ=W/V Equivalently, it may also be formulated as the product of density, Template:Mvar, and gravity acceleration, Template:Mvar: γ=ρg Its unit of measurement in the International System of Units (SI) is newton per cubic metre (N/m3), with base units of kgTemplate:Sdotm−2Template:Sdots−2. A commonly used value is the specific weight of water on Earth at Template:Convert, which is Template:Convert.[1]

Discussion

The density of a material is defined as mass divided by volume, typically expressed in units of kg/m3. Unlike density, specific weight is not a fixed property of a material, as it depends on the value of the gravitational acceleration, which varies with location (e.g., Earth's gravity). For simplicity, the standard gravity (a constant) is often assumed, usually taken as Template:Val.

Pressure may also affect values, depending upon the bulk modulus of the material, but generally, at moderate pressures, has a less significant effect than the other factors.[2]

Applications

Fluid mechanics

In fluid mechanics, specific weight represents the force exerted by gravity on a unit volume of a fluid. For this reason, units are expressed as force per unit volume (e.g., N/m3 or lbf/ft3). Specific weight can be used as a characteristic property of a fluid.[2]

Soil mechanics

Specific weight is often used as a property of soil to solve earthwork problems.

In soil mechanics, specific weight may refer to:

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Civil and mechanical engineering

Specific weight can be used in civil engineering and mechanical engineering to determine the weight of a structure designed to carry certain loads while remaining intact and remaining within limits regarding deformation.

Specific weight of water

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Specific weight of water at standard sea-level atmospheric pressure (Metric units) [2]
Temperature(°C) Specific weight (kN/m3)
0 9.805
5 9.807
10 9.804
15 9.798
20 9.789
25 9.777
30 9.765
40 9.731
50 9.690
60 9.642
70 9.589
80 9.530
90 9.467
100 9.399
Specific weight of water at standard sea-level atmospheric pressure (English units) [2]
Temperature(°F) Specific weight (lbf/ft3)
32 62.42
40 62.43
50 62.41
60 62.37
70 62.30
80 62.22
90 62.11
100 62.00
110 61.86
120 61.71
130 61.55
140 61.38
150 61.20
160 61.00
170 60.80
180 60.58
190 60.36
200 60.12
212 59.83

Specific weight of air

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Specific weight of air at standard sea-level atmospheric pressure (Metric units) [2]
Temperature(°C) Specific weight (N/m3)
−40 14.86
−20 13.86
0 12.68
10 12.24
20 11.82
30 11.43
40 11.06
60 10.4
80 9.81
100 9.28
200 7.33
Specific weight of air at standard sea-level atmospheric pressure (English units) [2]
Temperature(°F) Specific Weight (lbf/ft3)
−40
−20 0.0903
0 0.08637
10 0.08453
20 0.08277
30 0.08108
40 0.07945
50 0.0779
60 0.0764
70 0.07495
80 0.07357
90 0.07223
100 0.07094
120 0.06849
140 0.0662
160 0.06407
180 0.06206
200 0.06018
250 0.05594

References

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External links

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  1. National Council of Examiners for Engineering and Surveying (2005). Fundamentals of Engineering Supplied-Reference Handbook (7th ed.). Template:ISBN.
  2. a b c d e f Finnemore, J. E. (2002). Fluid Mechanics with Engineering Applications. New York: McGraw-Hill. Template:ISBN.