The absolute meter-kilogram-second system is a system of mechanical units. The meter is the base unit of length or distance, the kilogram is chosen to be a unit of mass, and the second is the base unit of time. All other mechanical quantities, and specifically force, are expressed in terms of combinations of these three units. In absolute systems, Newton's second law is expressed as F = ma, and since acceleration is the second derivative of a distance with respect to time, if the unit of length or distance is denoted by L, the unit of mass by M, and the unit of time by T, the unit of force becomes a derived unit of dimensions MLT−2, in this case kilogram·meter/second2, which is known as the newton.

Three approaches to mass and force units[1][2]

v · d · e


force, length, time weight, length, time mass, length, time
Force (F) F = m·a = w·a/g F = m·a/gc = w·a/g F = m·a = w·a/g
Weight (w) w = m·g w = m·g/gc ≈ m w = m·g
Acceleration (a) ft/s2 m/s2 ft/s2 m/s2 ft/s2 gal m/s2 m/s2
Mass (m) slug hyl, also called “metric slug” or “TME” lbm kg lb g t kg
Force (F) lb kp lbF kp pdl dyn sn N
Pressure (p) lb/in2 at PSI atm pdl/ft2 Ba pz Pa

International System of Units (SI)Edit

The SI is basically an example of an absolute meter-kilogram-second system, but with a number of additional units, which are used in decribing quantities outside of mechanics, to complete the system.

SI base units
Name Symbol Quantity
kilogram kg Mass
second s Time
meter m Length
ampere A Electrical current
kelvin K Temperature
mole mol Amount of substance
candela cd Luminous intensity

See also


  1. Lindeburg, Michael, Civil Engineering Reference Manual for the PE Exam 
  2. Wurbs, Ralph A, Fort Hood Review Sessions for Professional Engineering Exam,, retrieved October 26, 2011 

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