Fluid statics also termed as hydrostatics is the branch of fluid mechanics that deals with the study of fluids at rest, the pressure in a fluid or the pressure exerted by a fluid on an immersed body.
The velocity gradient which is the change of velocity between adjacent fluid layers divided by the distance between the layers will be zero.
The shear stress will also be equal to zero.
This means that there will not be any relative motion between adjacent and neighboring fluid layers. Since the fluid is considered to be at rest when we deal with fluid statics there will be only force due to pressure of fluid normal to the surface and force due to gravity acting on the fluid particles.
The main principles of fluid statics are Pascal’s law and Archimedes’ principle. The main reason for us to study about fluid statics is that it allows us to understand why some bodies float on water, why a closed plastic bottle, when kept at the bottom of water body, doesn’t remain there but comes to the top of the surface, why some bodies submerge while others don’t and many more interesting doubts can be easily resolved by understanding the concepts of fluid statics.
The reason for any object to experience an upward force when immersed in a fluid is called buoyancy.
The stability of submerged and floating bodies is dependent on the position of the center of gravity, the center of buoyancy and the weight of the body. These positions will determine if the body will remain in stable, unstable or neutral equilibrium. The study of fluid statics allows us to decide which fluid is suitable for the required condition.