# DoE Fundamentals Handbook- Thermodynamics, Heat Transfer and Fluid Flow

[document] Submitted on 27 April, 2017 - 23:21
Keywords

According to Newton’s Second Law of Motion, force (F) = ma, where a is acceleration. For example, on earth an object has a certain mass and a certain weight. When the same object is placed in outer space, away from the earth’s gravitational field, its mass is the same, but it is now in a "weightless" condition (that is, gravitational acceleration and, thus, force equal zero). The English system uses the pound-force (lbf) as the unit of weight. Knowing that acceleration has the units of ft/sec2 and using Newton’s second law, we can determine that the units of mass are lbf-sec2/ft. For simplification, 1 lbf-sec2/ft is called a slug. The basic unit of mass in the English system is the slug. However, the slug is an almost meaningless unit for the average individual. The unit of mass generally used is the pound-mass (lbm). In order to allow lbm to be used as a unit of mass, we must divide Newton’s second law by the gravitational constant (gc).

Defines standard
Replaced/Superseded by document(s)
Cancelled by
Amended by