a branch of physics that studies the motion of fluids and their interaction with solid bodies and external forces (e.g., gravity or pressure)
Formula for pressure as the ratio of force to surface area
Pressure is the force acting on each unit of area. The smaller the contact area for the same force, the higher the pressure created. The unit of measurement is Pascal (Pa).
Formula for fluid pressure at a depth: product of density, acceleration due to gravity, and depth
This pressure is created in a fluid due to its weight. The deeper, the greater the height of the fluid column — and the higher the pressure. It depends on the density of the substance, the acceleration due to gravity, and the depth of the point.
Formula for volumetric fluid flow rate as the product of flow velocity and cross-sectional area
The formula shows how much fluid volume passes through a cross-section per unit of time. The flow rate depends on the flow velocity and the cross-sectional area of the pipe. Units of measurement — m³/s.
Formula for continuity of fluid flow in sections with varying cross-section
If the fluid flow is conserved, then as the pipe narrows, the velocity increases. This formula reflects the law of conservation of volume: what goes in, comes out.
Bernoulli's formula: the sum of pressure, kinetic and potential energy in a flow section remains constant
Bernoulli's equation expresses the conservation of the total energy of a flow: the sum of pressure, kinetic energy, and potential energy is conserved along the stream.
Applicable to an ideal fluid (without viscosity), the flow must be steady.
The higher the velocity — the lower the pressure, and vice versa. This effect is the basis of aircraft operation, carburetors, and hydraulic systems.
When external pressure is applied to a fluid (or gas) in a closed volume, it is transmitted undiminished in all directions and to every point of the volume.
Thanks to Pascal's law, hydraulic presses, brakes, jacks, and other systems work. A small force over a small area can be transmitted as a large force over a large area, without pressure loss.
💡 Pascal's law can also be considered a consequence of the law of conservation of energy: pressure does not disappear or appear arbitrarily, but is merely transmitted. Moreover, it is valid not only for liquids but also for compressible media — for example, gases.