Understanding Pressure in Fluid Mechanics- Absolute and Gauge Pressure

Pressure is mathematically written as Force divided area. SI unit of Pressure is Pascal or Newton per meter square. At absolute vacuum, the pressure is 0. The pressure of the atmosphere above absolute vacuum is known as atmospheric pressure. The pressure from absolute vacuum to a pressure above atmospheric pressure is known as absolute pressure. If we subtract atmospheric pressure from absolute pressure we get gage pressure. If the absolute pressure is below atmospheric pressure, then the pressure value just below the atmospheric pressure is vacuum pressure.

Pressure is a scalar quantity. For a fluid at rest, pressure at a point is equal in all directions. Pressure in a fluid at rest does not change in the horizontal direction only varies with depth. Pascal's law states that when there is an increase in pressure at any point in a confined fluid, there is an equal increase at every other point in the container.

Chapters:
0:00 Introduction with examples
0:26 Pressure vs Normal Stress
1:30 Units of Pressure
2:13 Absolut, Gage, Atmospheric and Vacuum Pressure
3:20 Pressure at a point
6:00 Variation of Pressure with Depth
6:41 Pascal's Law
7:19 Application of Pascal's law
8:26 Design of Pressure Cooker Petcock