Class 11 Physics: Mechanical Properties of Fluids

Section A - 1 Mark Questions

1. Streamline Shape of Cars and Aeroplanes

   • Purpose: Minimize backward drag of atmosphere.

2. Sharp vs. Blunt Knife

   • Sharp edge has less area, resulting in higher pressure and easier cutting.

3. Streamlines Intersection

   • Impossible due to conflicting flow directions.

4. Insects on Water Surface

   • Surface tension acts like an elastic membrane supporting insects.

5. Pressure Calculation Example

   • Formula: Pressure = Force / Area
   • Example: 100 N force on 4 m² = 25 Pa

6. Straw Functionality

   • Low pressure in straw allows atmospheric pressure to push liquid up.

7. Atmospheric Pressure

   • Defined by air exertion due to gravity on Earth's surface.

8. Buoyant Force

   • Object floats if buoyant force ≥ weight; sinks if less.

9. Viscosity in Lubricants

   • High viscosity prevents lubricant from being squeezed out.

10. Temperature Effect on Liquids

    • Hotter liquids have lower viscosity, moving faster.

Section B - 2 Marks Questions

11. Walking on Soft Sand

    • Flat shoes distribute weight, reducing pressure and sinking.

12. Pressure in Vessels

    • Order: D > B > A > C based on water column height.

13. Pressure Definition

    • Pressure = Force/Area (Unit: Pascal)
    • Depends on force and contact area.

14. Pressure on Femur

    • Example calculation using mass and cross-sectional area.

15. Hydraulic Lift Maximum Pressure

    • Calculation for lifting 3000 kg using piston area.

16. Force to Pull Glass Plates

    • Example with oil viscosity and speed to determine force.

Detailed Concepts

Fluid Mechanics

• Fluids: Substances like liquids and gases that flow.
• Assumptions: Incompressible and non-viscous.

Fluid Statics

• Fluid Pressure

  • Normal force per unit area.
  • SI Unit: Pascal.

• Pressure Relations

  • Horizontal pressure consistency.
  • Vertical and acceleration effects on pressure.

• Atmospheric Pressure: Normal value at sea level is 1 atm.

• Pascal's Law: Pressure applied to a fluid is transmitted equally.

• Archimedes Principle: Buoyant force equals the weight of displaced fluid.

Fluid Dynamics

• Steady Flow: Velocity consistency in fluid particles.
• Equation of Continuity: Mass flow rate consistency in incompressible fluids.
• Bernoulli's Theorem: Energy conservation in fluid flow.

Viscosity

• Definition: Resistance to relative motion between fluid layers.
• Stokes Law: Viscous drag on spherical bodies.
• Terminal Velocity: Maximum velocity in viscous medium.
• Poiseuille’s Formula: Flow rate in capillaries.

Surface Tension

• Surface Energy and Pressure: Energy per unit area and pressure differences.
• Capillary Action: Rise/fall in narrow tubes due to adhesion and cohesion.

Additional Concepts

• Law of Floatation: Conditions for floating/sinking based on weight and buoyant force.
• Density and Mixture Calculations: Understanding density relations in mixtures.

Example Problems

• Pressure Calculation in Vessels: Combines density and liquid height to find pressure.