If the pressure is less than the local atmospheric pressure, we say that the pressure is negative gauge pressure or vacuum. Difference between absolute and gauge pressure.
Velocity is a vector quantity.
When the velocity of the fluid is not changing at one point, this condition is called steady-flow . The density of a liquid is approximately constant if there is no change in phase. If a fluid has a m that is independent of velocity, this fluid is called a Newtonian fluid . Other types of fluid are shown in the diagram below. Other non-Newtonian fluids are illustrated in the graph below.