Physics
13
Fluids
11
⚡ Quick Summary
Fluids are substances that can flow, including liquids and gases. Liquids have a fixed volume but can change shape easily. Gases can easily change both shape and volume.
['P = Lim (∆S→0) F/∆S']
Fluids
Matter is broadly divided into solid, liquid, and gas. Liquids and gases are called fluids.
For the purposes of this chapter, liquids are assumed to be incompressible (density is constant) and nonviscous (no tangential forces between layers).
Pressure in a Fluid
Pressure at a point in a fluid is defined as the force acting per unit area.
P = Lim (∆S→0) F/∆S.
For a homogeneous and nonviscous fluid, pressure is a scalar quantity.
SI unit of pressure is N/m2, called Pascal (Pa).
Variation of Pressure with Height
Consider two points A and B separated by a small vertical height dz.
Let the pressure at surface A be P and pressure at B be P + dP.