Pressure of Solids vs Liquids
Pressure is a very important concept in physics. The concept of pressure plays a very important role in applications such as thermodynamics, aerodynamics, fluid mechanics, deformations and many more. It is vital to have a good understanding of pressure in order to excel in any field that uses pressure as a base concept. In this article, we are going to discuss what pressure is, what pressure on liquids and pressure of solids are, their applications, the definitions of these two, applications of pressure of liquids and pressure of solids, and finally the differences of pressure of solids and liquids.
Pressure of Liquids
To understand the concept of pressure of liquids, one must first understand the concept of pressure in general. The pressure of a static fluid is equal to the weight of the fluid column above the point the pressure is measured. Therefore, the pressure of a static (non-flowing) fluid is dependent only of the density of the fluid, the gravitational acceleration, the atmospheric pressure and the height of the liquid above the point the pressure is measured. The pressure can also be defined as the force exerted by the collisions of particles. In this sense, the pressure can be calculated using the molecular kinetic theory of gasses and the gas equation. The term “hydro” means water and the term “static” means non-changing. This means hydrostatic pressure is the pressure of the non-flowing water. However, this is also applicable to any fluid including gasses. Since the hydrostatic pressure is the weight of the fluid column above the measured point it can be formulated using P= hdg, where P is the hydrostatic pressure, h is the height of the surface of the fluid form the measured point, d is the density of the fluid and g is the gravitational acceleration. The total pressure on the measured point is the unison of the hydrostatic pressure and the external pressure (i.e. atmospheric pressure) on the fluid surface. The pressure due to a moving fluid varies from that of a static fluid. The Bernoulli theorem is used to calculate the dynamic pressure of non-turbulent incompressible fluids.
Pressure of Solids
The pressure of a solid can also be interpreted using the argument based on liquid pressure. The atoms inside a solid can be considered static. Therefore, no pressure is created by the momentum change of a solid. But the weight of the solid column above a certain point is effective on the said point. Therefore, a pressure inside a solid can appear. However, solids do not expand or contract by large amounts due to this pressure. The pressure on the side of the solid normal to the weight vector is always zero. Therefore, the solid has its own shape unlike liquids, which take the shape of the container.
What is the difference between Pressure in Solids and in Liquids?
• Pressure inside liquids are due to the random movement of the liquid molecules and the weight of the liquid. The pressure inside solids occurs only due to the weight of the solid.
• The liquid pressure acts on the sides of the liquid as well as the bottom. The pressure due to solids only appears at the bottom of the solid.