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POUND MASS vs. POUND FORCE (lbm vs. lbf)
POUND MASS vs. POUND FORCE (lbm vs. lbf)
Published: 2014/04/07
Channel: Simply Engineering
Pound Force to Pound Mass Conversion : Physics & Math
Pound Force to Pound Mass Conversion : Physics & Math
Published: 2013/10/06
Channel: eHowEducation
How Much Force to Rupture a Spleen: Sport Science
How Much Force to Rupture a Spleen: Sport Science
Published: 2014/07/15
Channel: Your Discovery Science
Pound-force (lbf) vs Pound-mass (lbm) vs Slugs
Pound-force (lbf) vs Pound-mass (lbm) vs Slugs
Published: 2014/11/09
Channel: Boom of Prejudice
Pound Mass versus Pound Force
Pound Mass versus Pound Force
Published: 2015/01/28
Channel: APMonitor.com
World
World's Heaviest Weight
Published: 2017/05/24
Channel: Veritasium
How to Convert Newton Meters to Pound Force Feet : Conversions & Other Math Tips
How to Convert Newton Meters to Pound Force Feet : Conversions & Other Math Tips
Published: 2013/01/09
Channel: eHowEducation
Fight Science ( Martial Arts of Kicks )
Fight Science ( Martial Arts of Kicks )
Published: 2014/08/16
Channel: ต้นไม้เล่าเรื่อง - TreeTalk
Showing Off My 220 Pound Magnet
Showing Off My 220 Pound Magnet
Published: 2016/05/09
Channel: James Ray
What`s a "psi"?
What`s a "psi"?
Published: 2014/07/21
Channel: apprenticemath
Pound (force)
Pound (force)
Published: 2014/09/30
Channel: Audiopedia
Pound-force Meaning
Pound-force Meaning
Published: 2015/04/20
Channel: SDictionary
Explaining mass and force units
Explaining mass and force units
Published: 2014/01/27
Channel: Brittany Minnich
Pound (force)
Pound (force)
Published: 2016/01/29
Channel: WikiAudio
2000 pound force
2000 pound force
Published: 2017/07/29
Channel: dats fomino
Pound Force, Kilogram Force and Gravitational Constant - Applied Fluid Dynamics - Class 006
Pound Force, Kilogram Force and Gravitational Constant - Applied Fluid Dynamics - Class 006
Published: 2015/09/24
Channel: Chemical Engineering Guy
Frank Stea
Frank Stea's punch inflicts 1,394lbs of force. Undeniable PROOF!!!!!
Published: 2011/04/23
Channel: Frank Stea
Pounds per square inch
Pounds per square inch
Published: 2014/08/30
Channel: Audiopedia
Steel Bender
Steel Bender's Helper™ Ratings: Pounds of Force Required to Bend Them
Published: 2017/05/23
Channel: Primal Punch
How Much Force Does It Take To Break A Bone?
How Much Force Does It Take To Break A Bone?
Published: 2016/10/20
Channel: Seeker
Pound force/KG force/KG Weight concepts TA0104
Pound force/KG force/KG Weight concepts TA0104
Published: 2017/11/04
Channel: Technical Atyachar
Determine the shortest cable ABC that can be used to lift the beam
Determine the shortest cable ABC that can be used to lift the beam
Published: 2016/10/18
Channel: FinalAnswer
Apply Force Units
Apply Force Units
Published: 2014/08/10
Channel: Donald Elger
Trouble (The TEA/TEB Song), Mad Malts Brewing, April 23, 2016
Trouble (The TEA/TEB Song), Mad Malts Brewing, April 23, 2016
Published: 2016/04/27
Channel: Foot Pound Force
Resolve the 30-lb force into components along the u and v axes
Resolve the 30-lb force into components along the u and v axes
Published: 2016/10/09
Channel: FinalAnswer
How To : Convert Inch-lbs & Foot-lbs
How To : Convert Inch-lbs & Foot-lbs
Published: 2014/04/08
Channel: Real Tool Reviews
How much force to throw a 60 lb thing over a wall?
How much force to throw a 60 lb thing over a wall?
Published: 2017/07/14
Channel: Rhett Allain
POUND FORCE - ALAN DUNCAN MP GETS A NEW GARDEN FEATURE
POUND FORCE - ALAN DUNCAN MP GETS A NEW GARDEN FEATURE
Published: 2009/05/14
Channel: dontpanicmedia
So  it took 121,610 pounds of force =30,402.5 psi
So it took 121,610 pounds of force =30,402.5 psi
Published: 2017/11/08
Channel: Kulish Design Co., LLC
Alan Duncan Pound Force
Alan Duncan Pound Force
Published: 2011/07/06
Channel: Don't Panic London
My New Magnet Fishing Magnet 500 LB Holding Force Will It Lift A 315 LB Man?
My New Magnet Fishing Magnet 500 LB Holding Force Will It Lift A 315 LB Man?
Published: 2017/02/06
Channel: Jiggs Outdoors
2,000 ft/lbs torque wrench
2,000 ft/lbs torque wrench
Published: 2013/03/15
Channel: burn740
Resolve this force into components acting along members AB and AC
Resolve this force into components acting along members AB and AC
Published: 2016/10/09
Channel: FinalAnswer
Foot Pound Force - Bacon Machine
Foot Pound Force - Bacon Machine
Published: 2013/09/02
Channel: Dragoncon FilkTrack
Know Huntsville - Foot Pound Force - Bacon Machine
Know Huntsville - Foot Pound Force - Bacon Machine
Published: 2015/04/28
Channel: Know Huntsville
DragonForce - Operation Ground And Pound [OFFICIAL VIDEO]
DragonForce - Operation Ground And Pound [OFFICIAL VIDEO]
Published: 2006/08/18
Channel: Roadrunner Records
1N = x pound-force
1N = x pound-force
Published: 2017/10/04
Channel: Jordin
David Hewitt (Foot Pound Force) answers "What is Filk?"
David Hewitt (Foot Pound Force) answers "What is Filk?"
Published: 2014/05/24
Channel: Dragoncon FilkTrack
That punch tho👊💪 344 pounds of force
That punch tho👊💪 344 pounds of force
Published: 2016/01/08
Channel: Mohammed Ahmar
75 pound Force compound bow
75 pound Force compound bow
Published: 2016/08/05
Channel: Hank Williams
Know Huntsville - Foot Pound Force
Know Huntsville - Foot Pound Force
Published: 2015/04/20
Channel: Know Huntsville
Lion bite force : 600 pounds, Tiger bite force :1000 pounds
Lion bite force : 600 pounds, Tiger bite force :1000 pounds
Published: 2009/09/02
Channel: TigerFacts
Dj Snoopy ft. Lb - Undercover Lover (Official Video) | Shot By: Liquidartsmedia
Dj Snoopy ft. Lb - Undercover Lover (Official Video) | Shot By: Liquidartsmedia
Published: 2017/06/22
Channel: LiquidArtsMedia
Related lbm to lbf on earth
Related lbm to lbf on earth
Published: 2014/08/11
Channel: Donald Elger
Air Rifle Restrictions - 12 ft/lbs Explained
Air Rifle Restrictions - 12 ft/lbs Explained
Published: 2014/10/29
Channel: EnglishShooting
[Killing Floor]Fag pound forces you to ... (?)
[Killing Floor]Fag pound forces you to ... (?)
Published: 2009/07/25
Channel: leone123029
Foot-pound Force - Zombie Prostitute
Foot-pound Force - Zombie Prostitute
Published: 2015/04/05
Channel: H. Kyoht Luterman
How to use a Torque Wrench
How to use a Torque Wrench
Published: 2016/07/22
Channel: Mark's Garage
Neodymium Magnet Lifting 190 pounds
Neodymium Magnet Lifting 190 pounds
Published: 2008/06/30
Channel: robgallagher
Crushing A Baseball With 100,000 lbs Of Force
Crushing A Baseball With 100,000 lbs Of Force
Published: 2014/04/25
Channel: videoeoo vid
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WIKIPEDIA ARTICLE

From Wikipedia, the free encyclopedia
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Pound-force
Unit system English Engineering units, British Gravitational System
Symbol lbf 
Unit conversions
1 lbf in ... ... is equal to ...
   SI units    4.448222 N
   CGS units    444,822.2 dyn
   Absolute English System    32.17405 pdl

The pound-force (symbol: lbf[1], sometimes lbf,[2]) is a unit of force used in some systems of measurement including English Engineering units and the British Gravitational System.[3] Pound force should not be confused with foot-pounds or pound-feet, which are units of torque, and may be written as "lbf⋅ft". They should not be confused with pound-mass (symbol: lb), often simply called pounds, which is a unit of mass.

Definitions[edit]

The pound-force is equal to the gravitational force exerted on a mass of one avoirdupois pound on the surface of Earth. Since the 18th century, the unit has been used in low-precision measurements, for which small changes in Earth's gravity (which varies from place to place by up to half a percent) can safely be neglected.[4]

The 20th century, however, brought the need for a more precise definition. A standardized value for acceleration due to gravity was therefore needed.

Product of avoirdupois pound and standard gravity[edit]

The pound-force is the product of one avoirdupois pound (exactly 0.45359237 kg) and the standard acceleration due to gravity, 9.80665 m/s2 (about 32.174049 ft/s2).[5][6][7]

The standard values of acceleration of the standard gravitational field (gn) and the international avoirdupois pound (lb) result in a pound-force equal to 4.4482216152605 N:[8]

This definition can be rephrased in terms of the slug. A slug has a mass of 32.174049 lb. A pound-force is the amount of force required to accelerate a slug at a rate of 1 ft/s2, so:

Conversion to other units[edit]

Units of force
newton
(SI unit)
dyne kilogram-force,
kilopond
pound-force poundal
1 N ≡ 1 kg⋅m/s2 = 105 dyn ≈ 0.10197 kp ≈ 0.22481 lbf ≈ 7.2330 pdl
1 dyn = 10−5 N ≡ 1 g⋅cm/s2 ≈ 1.0197 × 10−6 kp ≈ 2.2481 × 10−6 lbf ≈ 7.2330 × 10−5 pdl
1 kp = 9.80665 N = 980665 dyn gn⋅(1 kg) ≈ 2.2046 lbf ≈ 70.932 pdl
1 lbf ≈ 4.448222 N ≈ 444822 dyn ≈ 0.45359 kp gn⋅(1 lb) ≈ 32.174 pdl
1 pdl ≈ 0.138255 N ≈ 13825 dyn ≈ 0.014098 kp ≈ 0.031081 lbf ≡ 1 lb⋅ft/s2
The value of gn as used in the official definition of the kilogram-force is used here for all gravitational units.

Foot–pound–second (FPS) systems of units[edit]

In some contexts, the term "pound" is used almost exclusively to refer to the unit of force and not the unit of mass. In those applications, the preferred unit of mass is the slug, i.e. lbf⋅s2/ft. In other contexts, the unit "pound" refers to a unit of mass. The international standard symbol for the pound as a unit of mass is lb.[9]

Three approaches to units of mass and force or weight[10][11]
Base Force Weight Mass
2nd law of motion m = F/a F = Wa/g F = ma
System BG GM EE M AE CGS MTS SI
Acceleration (a) ft/s2 m/s2 ft/s2 m/s2 ft/s2 gal m/s2 m/s2
Mass (m) slug hyl pound-mass kilogram pound gram tonne kilogram
Force (F),
weight (W)
pound kilopond pound-force kilopond poundal dyne sthène newton
Pressure (p) pound per square inch technical atmosphere pound-force per square inch atmosphere poundal per square foot barye pieze pascal

In the "engineering" systems (middle column), the weight of the mass unit (pound-mass) on Earth's surface is approximately equal to the force unit (pound-force). This is convenient because one pound mass exerts one pound force due to gravity. Note, however, unlike the other systems the force unit is not equal to the mass unit multiplied by the acceleration unit[12]—the use of Newton's Second Law, F = ma, requires another factor, gc, usually taken to be 32.174049 (lb⋅ft)/(lbf⋅s2). "Absolute" systems are coherent systems of units: by using the slug as the unit of mass, the "gravitational" FPS system (left column) avoids the need for such a constant. The SI is an "absolute" metric system with kilogram and meter as base units.

See also[edit]

Notes[edit]

  1. ^ IEEE Standard Letter Symbols for Units of Measurement (SI Units, Customary Inch-Pound Units, and Certain Other Units), IEEE Std 260.1™-2004 (Revision of IEEE Std 260.1-1993)
  2. ^ Fletcher, Leroy S.; Shoup, Terry E. (1978), Introduction to Engineering, Prentice-Hall, ISBN 978-0135018583, LCCN 77024142. :257
  3. ^ "Mass and Weight". engineeringtoolbox.com. 
  4. ^ Acceleration due to gravity varies over the surface of the Earth, generally increasing from about 9.78 m/s2 (32.1 ft/s2) at the equator to about 9.83 m/s2 (32.3 ft/s2) at the poles.
  5. ^ BS 350 : Part 1: 1974 Conversion factors and tables, Part 1. Basis of tables. Conversion factors. British Standards Institution. 1974. p. 43. 
  6. ^ In 1901 the third CGPM declared (second resolution) that:

    The value adopted in the International Service of Weights and Measures for the standard acceleration due to Earth's gravity is 980.665 cm/s2, value already stated in the laws of some countries.

    This value was the conventional reference for calculating the kilogram-force, a unit of force whose use has been deprecated since the introduction of SI.

  7. ^ Barry N. Taylor, Guide for the Use of the International System of Units (SI), 1995, NIST Special Publication 811, Appendix B note 24
  8. ^ The international avoirdupois pound is defined to be exactly 0.45359237 kg.
  9. ^ IEEE Std 260.1™-2004, IEEE Standard Letter Symbols for Units of Measurement (SI Units, Customary Inch-Pound Units, and Certain Other Units)
  10. ^ Comings, E. W. (1940). "English Engineering Units and Their Dimensions". Industrial & Engineering Chemistry. 32 (7): 984–987. doi:10.1021/ie50367a028. 
  11. ^ Klinkenberg, Adrian (1969). "The American Engineering System of Units and Its Dimensional Constant gc". Industrial & Engineering Chemistry. 61 (4): 53–59. doi:10.1021/ie50712a010. 
  12. ^ The acceleration unit is the distance unit divided by the time unit squared.

References[edit]

  • Obert, Edward F., “THERMODYNAMICS”, D.J. Leggett Book Company Inc., New York 1948; Chapter I, Survey of Dimensions and Units, pages 1-24.

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