The specific weight, also known as the unit weight (symbol γ, the Greek letter gamma), is a volume-specific quantity defined as the weight per unit volume of a material.
The specific weight, γ, of a material is defined as the product of its density, ρ, and the standard gravity, g:
The density of the material is defined as mass per unit volume, typically measured in kg/m3. The standard gravity is acceleration due to gravity, usually given in m/s2, and on Earth usually taken as 9.81 m/s2.
Unlike density, specific weight is not a fixed property of a material. It depends on the value of the gravitational acceleration, which varies with location. 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]
Applicationsedit
Fluid mechanicsedit
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 mechanicsedit
Specific weight is often used as a property of soil to solve earthwork problems.
In soil mechanics, specific weight may refer to:
Moist unit weight
The unit weight of a soil when void spaces of the soil contain both water and air.
The difference between the saturated unit weight and the unit weight of water.[4] It is often used in the calculation of the effective stress in a soil. The formula for submerged unit weight is:
where
γ′ is the submerged unit weight of the material
γs is the saturated unit weight of the material
γw is the unit weight of water
Civil and mechanical engineeringedit
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 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
Referencesedit
^National Council of Examiners for Engineering and Surveying (2005). Fundamentals of Engineering Supplied-Reference Handbook (7th ed.). ISBN1-932613-00-5.
^ abcdefFinnemore, J. E. (2002). Fluid Mechanics with Engineering Applications. New York: McGraw-Hill. ISBN0-07-243202-0.
^Das, Braja M. (2007). Principles of Geotechnical Engineering. Canada: Chris Carson. ISBN0-495-07316-4.
^The Transtec Group, Inc. (2012). Basic Definitions and Terminology of Soils. [1] (Page viewed December 7, 2012
specific, weight, confused, with, specific, gravity, specific, density, specific, force, specific, weight, also, known, unit, weight, symbol, greek, letter, gamma, volume, specific, quantity, defined, weight, unit, volume, material, commonly, used, value, spec. Not to be confused with Specific gravity Specific density or Specific force The specific weight also known as the unit weight symbol g the Greek letter gamma is a volume specific quantity defined as the weight per unit volume of a material A commonly used value is the specific weight of water on Earth at 4 C 39 F which is 9 807 kilonewtons per cubic metre or 62 43 pounds force per cubic foot 1 Contents 1 Definition 2 Applications 2 1 Fluid mechanics 2 2 Soil mechanics 2 3 Civil and mechanical engineering 3 Specific weight of water 4 Specific weight of air 5 References 6 External linksDefinition editThe specific weight g of a material is defined as the product of its density r and the standard gravity g g r g displaystyle gamma rho g nbsp The density of the material is defined as mass per unit volume typically measured in kg m3 The standard gravity is acceleration due to gravity usually given in m s2 and on Earth usually taken as 9 81 m s2 Unlike density specific weight is not a fixed property of a material It depends on the value of the gravitational acceleration which varies with location 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 editFluid mechanics edit 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 edit Specific weight is often used as a property of soil to solve earthwork problems In soil mechanics specific weight may refer to Moist unit weight The unit weight of a soil when void spaces of the soil contain both water and air g 1 w G s g w 1 e displaystyle gamma frac 1 w G s gamma w 1 e nbsp where g is the moist unit weight of the material gw is the unit weight of water w is the moisture content of the material Gs is the specific gravity of the solid e is the void ratio Dry unit weight The unit weight of a soil when all void spaces of the soil are completely filled with air with no water The formula for dry unit weight is g d G s g w 1 e g 1 w displaystyle gamma d frac G s gamma w 1 e frac gamma 1 w nbsp where g is the moist unit weight of the material gd is the dry unit weight of the material gw is the unit weight of water w is the moisture content of the material Gs is the specific gravity of the solid e is the void ratio Saturated unit weight The unit weight of a soil when all void spaces of the soil are completely filled with water with no air The formula for saturated unit weight is g s G s e g w 1 e displaystyle gamma s frac G s e gamma w 1 e nbsp where gs is the saturated unit weight of the material gw is the unit weight of water Gs is the specific gravity of the solid e is the void ratio 3 Submerged unit weight The difference between the saturated unit weight and the unit weight of water 4 It is often used in the calculation of the effective stress in a soil The formula for submerged unit weight is g g s g w displaystyle gamma gamma s gamma w nbsp where g is the submerged unit weight of the material gs is the saturated unit weight of the material gw is the unit weight of water Civil and mechanical engineering edit 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 editSee also Water density 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 83Specific weight of air editMain article Density of air 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 05594References edit National Council of Examiners for Engineering and Surveying 2005 Fundamentals of Engineering Supplied Reference Handbook 7th ed ISBN 1 932613 00 5 a b c d e f Finnemore J E 2002 Fluid Mechanics with Engineering Applications New York McGraw Hill ISBN 0 07 243202 0 Das Braja M 2007 Principles of Geotechnical Engineering Canada Chris Carson ISBN 0 495 07316 4 The Transtec Group Inc 2012 Basic Definitions and Terminology of Soils 1 Page viewed December 7 2012External links editSubmerged weight calculator Specific weight calculator http www engineeringtoolbox com density specific weight gravity d 290 html http www themeter net pesi spec e htm Retrieved from https en wikipedia org w index php title Specific weight amp oldid 1188515750, wikipedia, wiki, book, books, library,
