Here are notes on Mechanical Properties of Fluids written in a clear format suitable for adding to a website for Maharashtra Board HSC (Class 12) Physics – Chapter 2 📘. These notes follow the MSBSHSE syllabus and include key definitions, formulas, and explanations. (kitabcd.org)

Mechanical Properties of Fluids — HSC Physics Notes (Maharashtra Board)

1. What is a Fluid?

A fluid is a substance that flows and deforms continuously when an external force acts on it. Fluids include liquids and gases. (kitabcd.org)

Key characteristics:

• Fluids do not have a fixed shape.

• They take the shape of their container.

• They have zero shear modulus and begin to flow under shear stress. (kitabcd.org)

2. Pressure in Fluids

Pressure (p) is the force per unit area exerted by a fluid on a surface:

[
p = \frac{F}{A}
]

• SI unit: Pascal (Pa) = N/m²

• Atmospheric pressure: 1 atm = 1.013×10⁵ Pa. (kitabcd.org)

Types of Pressure

Absolute Pressure: Total pressure measured relative to a vacuum.
Gauge Pressure: Pressure measured relative to atmospheric pressure.
Hydrostatic Pressure: Pressure due to a fluid column depends on depth, not on shape of the container. (freemocktest.online)

3. Pascal’s Law

Pascal’s law states that a change in pressure applied to a confined fluid is transmitted equally and undiminished in all directions throughout the fluid and to the walls of its container. (kitabcd.org)

Applications:

• Hydraulic press

• Hydraulic lift

• Braking systems
  These use pressure transmission to multiply force. (kitabcd.org)

4. Surface Tension

Surface tension is the property of a liquid surface to behave like a thin stretched elastic membrane due to molecular forces. (kitabcd.org)

• Caused by cohesive forces between liquid molecules.

• Results in formation of drops and bubbles and causes capillary action. (kitabcd.org)

Facts about surface tension:

• Decreases with increasing temperature.

• Important in phenomena like a needle floating on water, capillary rise, and shapes of droplets. (kitabcd.org)

5. Viscosity

Viscosity is the internal friction in a fluid that resists its flow. (kitabcd.org)

• Fluids with high viscosity (like honey) flow slowly.

• Fluids with low viscosity (like water) flow more easily. (GeeksforGeeks)

Coefficient of Viscosity (η)

It measures the resistance to flow per unit velocity gradient in a fluid. (freemocktest.online)

Stokes’ Law

For a small sphere moving through a viscous fluid:

[
F = 6\pi \eta r v
]

where
F = viscous force,
η = coefficient of viscosity,
r = radius of sphere,
v = velocity of sphere. (kitabcd.org)

6. Fluids in Motion

Types of Flow

• Laminar (streamline) flow: Fluid particles move in smooth paths.

• Turbulent flow: Fluid particles move chaotically with eddies. (kitabcd.org)

Equation of Continuity

For an incompressible fluid in steady flow:

[
A_1 v_1 = A_2 v_2
]

where A is cross-sectional area and v is speed of fluid. (kitabcd.org)

7. Bernoulli’s Principle

In a flowing fluid, total energy per unit volume remains constant:
P + 1/2 ρv2 + ρgh = constant 

v

where
P = fluid pressure,
ρ = density,
v = velocity,
g = acceleration due to gravity,
h = height above reference. 

Applications: Venturi effect, lift on wings, fluid speed measurements. 

Summary

Mechanical properties of fluids describe how fluids behave at rest and in motion, including:

• Pressure and its types

• Pascal’s law and hydraulic systems

• Surface tension and its effects

• Viscosity and fluid resistance

• Flow continuity and Bernoulli’s principle 

Important Formulas 

• 1 full derivation from this chapter is very common
  
  

• Numericals = 8–10 marks guaranteed
  
  

• Surface tension & Bernoulli’s theorem are favorite areas

• Learn derivations + neat labelled diagrams
  
  

• Practice standard numericals only (board repeats pattern)
  
  

• Write units & formula first → full marks trick