engineering Engineering is the practice of using natural science, mathematics, and the engineering design process to Problem solving#Engineering, solve problems within technology, increase efficiency and productivity, and improve Systems engineering, s ...

and

physics Physics is the scientific study of matter, its Elementary particle, fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge whi ...

, ''g''_c is a unit conversion factor used to convert

mass Mass is an Intrinsic and extrinsic properties, intrinsic property of a physical body, body. It was traditionally believed to be related to the physical quantity, quantity of matter in a body, until the discovery of the atom and particle physi ...

force In physics, a force is an influence that can cause an Physical object, object to change its velocity unless counterbalanced by other forces. In mechanics, force makes ideas like 'pushing' or 'pulling' mathematically precise. Because the Magnitu ...

or vice versa. It is defined as :

g_\text = \frac

In unit systems where force is a

derived unit A base unit of measurement (also referred to as a base unit or fundamental unit) is a unit of measurement adopted for a '' base quantity''. A base quantity is one of a conventionally chosen subset of physical quantities, where no quantity in the ...

, like in

SI unit The International System of Units, internationally known by the abbreviation SI (from French ), is the modern form of the metric system and the world's most widely used system of units of measurement, system of measurement. It is the only system ...

s, ''g''_c is equal to 1. In unit systems where force is a primary unit, like in

imperial and US customary measurement systems The imperial and US customary measurement systems are both derived from an earlier English system of measurement which in turn can be traced back to Ancient Roman units of measurement, and Carolingian and Saxon units of measure. The US Custom ...

, ''g''_c may or may not equal 1 depending on the units used, and value other than 1 may be required to obtain correct results. For example, in the

kinetic energy In physics, the kinetic energy of an object is the form of energy that it possesses due to its motion. In classical mechanics, the kinetic energy of a non-rotating object of mass ''m'' traveling at a speed ''v'' is \fracmv^2.Resnick, Rober ...

(KE) formula, if ''g''_c = 1 is used, then KE is expressed in

foot-poundal The foot-poundal (symbol: ft-pdl) is a unit of energy, introduced in 1879, that is part of the Absolute English system of units, which itself is a coherent subsystem of the foot–pound–second system. Edward F. Obert, Thermodynamics, McGraw- ...

s; but if ''g''_c = 32.174 is used, then KE is expressed in

foot-pound The foot-pound force (symbol: ft⋅lbf, ft⋅lbf, or ft⋅lb ) is a unit of work or energy in the engineering and gravitational systems in United States customary and imperial units of measure. It is the energy transferred upon applying a ...

Motivations

According to

Newton's second law Newton's laws of motion are three physical laws that describe the relationship between the motion of an object and the forces acting on it. These laws, which provide the basis for Newtonian mechanics, can be paraphrased as follows: # A body re ...

, the

''F'' is proportional to the product of mass ''m'' and acceleration ''a'': :

F \propto ma

or :

F = K ma

If ''F'' = 1 lbf, ''m'' = 1 lb, and ''a'' = , then :

1~\text = K \cdot 1~\text \cdot 32.174~\frac

Leading to :

K = \frac = 0.03108~\frac

''g''_c is defined as the reciprocal of the constant ''K'' :

g_\text = \frac = 32.174~\frac

or equivalently, as :

g_\text = \frac

Specific systems of units

References

{{Reflist Equations