where t stands for time, m for mass, v for the velocity, and f for forces acting on the control mass.
We shall transform these laws into a control volume form that will be used throughout, this book. The fundamental variables will be intensive rather than extensive properties; the former are properties which are independent of the amount of matter considered. Examples are density p (mass per unit volume) and velocity v (momentum per unit mass).
If O is any conserved intensive property (for mass conservation, O = 1; for momentum conservation, O = v ; for conservation of a scalar, 11> represents the conserved property per unit mass), then the corresponding extensive property O can be expressed as: