Fluid Mechanics (Part-3) (General Engineering) (SSC JE)

Viscosity of gas–Viscosity of gas increases with increase in temperature due to molecular momentum exchange (MME) while viscosity of liquid decreases with increase in temperature.

Absolute pressure in flow system may be above, below or equal to local atmospheric pressure.
• It is necessary to establish an absolute pressure scale which is independent of the changes in atmospheric pressure.
• Any pressure measured above the absolute zero pressure is termed as an absolute pressure.

The continuity equation simply states that the total accumulation of mass from all phases is equal to the net flow of mass into the control volume plus the net amount of mass that enters the control volume from a source such as a well. This equation is based on principle of conservation of mass.

Kinematic viscosity of gases on increase of temperature increases because of increase in dynamic viscosity due to molecular collision

Attraction force between different molecules is known as adhesion. The mixing of other substances with water depends on the emulsion property which allows it to mix with water. The emulsion property of milk provided it very good adhesion.

Ideal fluid–Those fluids which are incompressible and non viscous with infinite bulk modulus, known as ideal fluids. Ideal fluids do not obey Newton's law of viscosity. Properties–
(i) Density of fluid is constant
(ii) Zero surface tension and frictionless
(iii) No shear resistance
(iv) Particle of fluid should be irrotational

Mercury is a liquid that shows a capillary depression.
Capillary depression - cohesion > Adhesion.
In case of mercury, cohesive forces are higher as compare to adhesive forces. Therefore, the molecules of mercy are more attracted towards its own molecules than the capillary walls. So, level of mercury will wall.