Thanks for help. I’ve been struggling to understand the term pressure because I would always think of directions… due to this definition: “it acts in all directions”. However, knowing that pressure is a scalar quantity, just like mass, I thought I should give it a different approach. Interestingly, when I did thermodynamics, the term pressure was perfectly intuitive to me (and still is when talking about gases), but with liquids it felt like a whole different story and I got lost. So I choose to apply thermodynamical approach to liquids too and that’s why I asked this question. I feel like I am slowly, but surely, connecting all information and knowledge I’ve gained so far about fluidsDale said:Yes. Is there some reason that isn’t clear to you?
If you person on the free surface with a spoon, the system will no longer be in equilibrium, and the spoon will begin descending into the fluid. The fluid at the surface of the spoon will be moving at the spoon velocity, while the fluid further away will be moving more slowly, and the fluid at the wall of the glass will not be moving. So the fluid will be deforming and, in terms of what Dale has pointed out, there will be viscous stresses developed within the deforming fluid, such that the state of stress is no longer isotropic.adjurovich said:Let’s imagine a glass of water. Now, we press on the free surface of water with a spoon (just for example), will the pressure in the entire glass increase equally?
The mental picture I have is of a spoon pressing down into the water without submerging. Like a tiny boat that is forced a bit into the water.Chestermiller said:If you [press] on the free surface with a spoon [...]
Fluid pressure is the force exerted by a fluid per unit area on a surface. It is caused by the weight of the fluid above the surface and acts in all directions. In liquids, pressure increases with depth due to the weight of the liquid above, and it can be measured in units such as pascals (Pa), atmospheres (atm), or pounds per square inch (psi).
Fluid pressure can be calculated using the formula: P = ρgh, where P is the pressure, ρ (rho) is the density of the fluid, g is the acceleration due to gravity, and h is the height (or depth) of the fluid column above the point where the pressure is being measured. This formula indicates that pressure increases with depth in a fluid.
Fluid pressure is primarily affected by the density of the fluid, the gravitational acceleration, and the depth of the fluid. Additionally, temperature can affect the density of the fluid, which in turn can influence the pressure. In non-static conditions, factors such as fluid motion and viscosity can also play a role in the pressure experienced within the fluid.
Fluid pressure increases linearly with depth in a liquid. As you go deeper into a fluid, the weight of the fluid above increases, resulting in higher pressure. This relationship is described by the hydrostatic pressure equation, and it shows that for every meter of depth in water, the pressure increases by approximately 9.81 kPa (kilopascals).
Absolute pressure is the total pressure measured relative to a perfect vacuum, while gauge pressure is the pressure measured relative to atmospheric pressure. Gauge pressure can be positive or negative, depending on whether the pressure is above or below atmospheric pressure. For example, a gauge pressure of 0 indicates that the pressure is equal to atmospheric pressure, while a negative gauge pressure indicates a vacuum condition.