Fluid Mechanics (Part-2) (General Engineering) (SSC JE)

Pitot tube–An instrument that is used for measuring velocity of flowing fluid at a point.

Adhesion–The tendency of two or more different molecules to bond with each other is known as adhesion.
Ex.–Paper + fevicol, water + glass etc.
Cohesion–The tendency of two or more having same nature and properties to bond with each other is known as cohesion.
Ex.–O₂ + H₂etc.
OR
"Attraction between same molecule is called cohesion and attraction between different molecules is called adhesion."

Cohesion–Attraction force between same kind of molecules is called as cohesion. Example–H₂O-H₂O, Hg-Hg etc.
Adhesion–Attraction force between different type of molecules is called as adhesion. Example–
1. Writing on a paper with pen
2. Wetting of glass plate by water
3. Glueing two surfaces together using fevicol.

Viscosity 'µ'–It is the measure of resistance of fluid between its layers. Viscosity of liquids is due to cohesion but for gases it is due to MME. MME–Molecular momentum exchange/transfer. Effect of temperature and pressure–
• Liquid → Temp ↑ µ↓ ; Pressure↑ µ = almost constant
• Gas→ Temp ↑ µ↑ ; Pressure↑ µ = almost same.