In engineering and physics, g_{c} is a unit conversion factor used to convert mass to force or vice versa.^{[1]} It is defined as
In unit systems where force is a derived unit, like in SI units, g_{c} is equal to 1. In unit systems where force is a primary unit, like in English units, g_{c} is not equal to 1, and is required to obtain correct results.^{[2]}
Motivations
According to Newton's law of motion, the force F is proportional to the product of mass m and acceleration a:
or
If F = 1 lbf, m = 1 lb, and a = 32.2 ft/s^{2}, then
Leading to
g_{c} is defined as the reciprocal of the constant K
or equivalently, as
Specific systems of units
International System | English System | British Customary System |
---|---|---|
g_{c} = 1 (kg·m)/(N·s^{2}) | g_{c} = 32.2 (lb·ft)/(lbf·s^{2}) | g_{c} = 1 (slug·ft)/(lbf·s^{2}) |
References
- ^ Janna, William (2015). Introduction to Fluid Mechanics (5th ed.). CRC Press. p. 5. ISBN 9781482211610.
- ^ Cengel, Yunus; Boles, Michael (2014). Thermodynamics: An Engineering Approach (8th ed.). McGraw-Hill Education. p. 6. ISBN 9780073398174.