Fluids are the substances which move or flow in a certain direction when an external force is applied to them. Fluids can be either gases or liquids. However, when you study fluids and their mechanical properties, you come across two topics namely hydrodynamics and hydrostatics.
Hydrostatic is concerned with fluids at rest while hydrodynamics deals with fluids which are in motion.
Pascal's Law: When a fluid is at rest, the pressure on the liquid is the same at all points provided, they are of the same height. The change in pressure which has been applied on the fluid which is enclosed can be transmitted undiminished to every point of the fluid and the container vessel's walls.
When an incompressible fluid is passing between every second in a pipe of non-uniform cross-section, the volume will be the same as the steady flow. Bernoulli's principle is an equation which states the conservation of energy of non-viscous fluid motion in a steady state.
Reynold's Number: Reynolds number is referred to the onset of turbulence in a fluid flow which can be determined by a dimensionless parameter.
Surface Tension: It is referred to the force per unit length which is acting on the plane of the interface between the bonding surface and the liquid. It is the amount of the extra energy which the molecules at the interface have when compared to the interior.