Fluids and Nonmagnetic Plasmas

Liquids, gases and plasmas may often be treated as a continuous media with a density, $\rho$, pressure, $p$, and velocity, ${\bf v}$, all functions of position and time.

$$\rho \hbox{ is the mass per unit volume } kg m^{-3} \qquad {M\over L^{3}}.$$ (2.1)

$$p \hbox{ is the pressure force per unit area } pascals \qquad {M\over L T^{2}}.$$ (2.2)

The pressure is the force per unit area that is exerted on a surface by the fluid or plasma.