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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
Pound Mass versus Pound Force
Pound Mass versus Pound Force
Published: 2015/01/28
Channel: APMonitor.com
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
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
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
2000 pound force
2000 pound force
Published: 2017/07/29
Channel: dats fomino
Explaining mass and force units
Explaining mass and force units
Published: 2014/01/27
Channel: Brittany Minnich
75 pound Force compound bow
75 pound Force compound bow
Published: 2016/08/05
Channel: Hank Williams
Alan Duncan Pound Force
Alan Duncan Pound Force
Published: 2011/07/06
Channel: Don't Panic London
Apply Force Units
Apply Force Units
Published: 2014/08/10
Channel: Donald Elger
Pound-force Meaning
Pound-force Meaning
Published: 2015/04/20
Channel: SDictionary
Know Huntsville - Foot Pound Force - Bacon Machine
Know Huntsville - Foot Pound Force - Bacon Machine
Published: 2015/04/28
Channel: Know Huntsville
Fight Science ( Martial Arts of Kicks )
Fight Science ( Martial Arts of Kicks )
Published: 2014/08/16
Channel: ต้นไม้เล่าเรื่อง - TreeTalk
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
Know Huntsville - Foot Pound Force
Know Huntsville - Foot Pound Force
Published: 2015/04/20
Channel: Know Huntsville
What`s a "psi"?
What`s a "psi"?
Published: 2014/07/21
Channel: apprenticemath
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 Does It Take To Break A Bone?
How Much Force Does It Take To Break A Bone?
Published: 2016/10/20
Channel: Seeker
Frank Stea
Frank Stea's punch inflicts 1,394lbs of force. Undeniable PROOF!!!!!
Published: 2011/04/23
Channel: Frank Stea
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
That punch tho👊💪 344 pounds of force
That punch tho👊💪 344 pounds of force
Published: 2016/01/08
Channel: Mohammed Ahmar
Foot Pound Force - Bacon Machine
Foot Pound Force - Bacon Machine
Published: 2013/09/02
Channel: Dragoncon FilkTrack
Pound (force)
Pound (force)
Published: 2014/09/30
Channel: Audiopedia
Airforce Texan 730 foot pound , 4500 psi  Upgrade from www.africanairordnance.com part 2
Airforce Texan 730 foot pound , 4500 psi Upgrade from www.africanairordnance.com part 2
Published: 2016/11/26
Channel: Jeremy King
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
DragonForce - Operation Ground And Pound [OFFICIAL VIDEO]
DragonForce - Operation Ground And Pound [OFFICIAL VIDEO]
Published: 2006/08/18
Channel: Roadrunner Records
Pound (force)
Pound (force)
Published: 2016/01/29
Channel: WikiAudio
Foot-pound Force - Zombie Prostitute
Foot-pound Force - Zombie Prostitute
Published: 2015/04/05
Channel: H. Kyoht Luterman
Tizzy Stackz - Zoomin (ft. LB)
Tizzy Stackz - Zoomin (ft. LB)
Published: 2017/07/01
Channel: 24MG
Related lbm to lbf on earth
Related lbm to lbf on earth
Published: 2014/08/11
Channel: Donald Elger
Converting Force Pounds to Foot Pound of Max Torque
Converting Force Pounds to Foot Pound of Max Torque
Published: 2016/02/09
Channel: Crown Oilfield Instrumentation
Foot-pound (energy)
Foot-pound (energy)
Published: 2016/01/22
Channel: WikiAudio
How to Convert the Torque From Foot-Pounds : Science & Math
How to Convert the Torque From Foot-Pounds : Science & Math
Published: 2013/10/05
Channel: eHowEducation
How to Convert Inch-Pounds to Newton-Meters : Conversions & Other Math Tips
How to Convert Inch-Pounds to Newton-Meters : Conversions & Other Math Tips
Published: 2013/01/20
Channel: eHowEducation
Minn Kota Endura c2 55 lb thrust on 14 ft v-hull
Minn Kota Endura c2 55 lb thrust on 14 ft v-hull
Published: 2013/06/04
Channel: BassQuatchin Pa
Foot-pound Force - I
Foot-pound Force - I'm Going To Try Science
Published: 2015/04/05
Channel: H. Kyoht Luterman
Pounds per square inch
Pounds per square inch
Published: 2014/08/30
Channel: Audiopedia
Foot-pound Force - Little Red Button
Foot-pound Force - Little Red Button
Published: 2015/04/05
Channel: H. Kyoht Luterman
Steel Bender
Steel Bender's Helper™ Ratings: Pounds of Force Required to Bend Them
Published: 2017/05/23
Channel: Primal Punch
Foot-pound Force - Craft Beer Nerds
Foot-pound Force - Craft Beer Nerds
Published: 2015/04/05
Channel: H. Kyoht Luterman
Ivy - One-Pound Force of Life - Sight-Impaired CH Kitten
Ivy - One-Pound Force of Life - Sight-Impaired CH Kitten
Published: 2012/10/15
Channel: Jennifer McCollum
HolliStar V2 Rocket Engine Tests 50 pounds of force
HolliStar V2 Rocket Engine Tests 50 pounds of force
Published: 2014/09/24
Channel: Jared Brewer
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
How to use a Torque Wrench
How to use a Torque Wrench
Published: 2016/07/22
Channel: Mark's Garage
Converting Feet to PSI
Converting Feet to PSI
Published: 2015/12/14
Channel: FranklinWater
Dirtbike LB ft Young Adz - Bragging Rights @DIRTBIKE_LB @YoungAdz1
Dirtbike LB ft Young Adz - Bragging Rights @DIRTBIKE_LB @YoungAdz1
Published: 2017/02/11
Channel: RayleighSho
How to read and set a torque wrench (ft-lb and Nm)
How to read and set a torque wrench (ft-lb and Nm)
Published: 2012/09/29
Channel: apprenticemath
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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. Today, in accordance with the General Conference on Weights and Measures, standard gravity is usually taken to be 9.80665 m/s2 (about 32.174 049 ft/s2).[5][6]

The acceleration of the standard gravitational field (gn) and the international avoirdupois pound (lb) define the pound-force as 4.4482216152605 N:[7]

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:

1 lb m ∗1 slug/32.2 lb m ∗32.2ft/s^2 =1 lb f

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.[8]

Three approaches to units of mass and force or weight
Base units Force, length, time Weight, length, time Mass, length, time
2nd Law of Motion m = F/a F = wa/gc 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 lb kg lb g t kg
Force (F),
Weight (w)
lb kp pdl dyn sn N
Pressure (p) lb/in2 at psi atm pdl/ft2 Ba pz Pa

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[9]—the use of Newton's Second Law, F = m·a, 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 and 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.
  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. ^ 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.

  6. ^ Barry N. Taylor, Guide for the Use of the International System of Units (SI), 1995, NIST Special Publication 811, Appendix B note 24
  7. ^ The international avoirdupois pound is defined to be exactly 0.45359237 kg.
  8. ^ IEEE Std 260.1™-2004, IEEE Standard Letter Symbols for Units of Measurement (SI Units, Customary Inch-Pound Units, and Certain Other Units)
  9. ^ The acceleration unit is the distance unit divided by the time unit squared.

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