Table of Contents
- What is fluid?
- Important characteristics of fluids:
- Difference between liquid and gases:
- Fluid statics
- Fluid dynamics
What is fluid?
A fluid is a substance that can flow. It ultimately assumes the shape of the containing vessel because it cannot withstand shearing stress. Thus, both liquids and gases are fluids.
Important characteristics of fluids:
(i) The atoms or molecules in a fluid are arranged in a random manner.
(ii) A fluid cannot withstand tangential or shearing stress for an indefinite period. It begins to flow when a shearing stress is applied.
(iii) A fluid has no definite shape of its own. It ultimately assumes the shape of the containing vessel. So a fluid has no modulus of rigidity.
(iv) A fluid can exert/withstand a force in a direction perpendicular to its surface. So a fluid does have a bulk modulus of rigidity.
Difference between liquid and gases:
A liquid is incompressible and has a definite volume and a free surface of its own. A gas is compressible, and it expands to occupy all the space available to it.
Fluid statics
The branch of physics that deals with the study of fluids at rest is called fluid statics or hydrostatics. Its study includes hydrostatic pressure, Pascal’s law, Archimedes’ principle, floatation of bodies and surface tension.
Fluid dynamics
The branch of physics that deals with the study of fluids in motion is called fluid dynamics or hydrodynamics. Its study includes equation of continuity, Bernoulli’s theorem, Torricelli’s theorem, viscosity, etc.