NEB Class 12 Physics Fluid statics Notes in PDF Complete Handwritten. Physics Notes 2081: All Chapters | New Curriculum | Class 12 Physics Notes download.
Mero Enotes is a simple educational Website Built to help Class 11 and 12 students excel in their studies. We offer Notes, question papers, and important study materials across various subjects for both science and management faculties. Whether youβre looking for Physics, Chemistry, Biology, Accounting, Economics, and Finance, Mero Enotes provides organized PDF resources, embedded via Google Drive for easy access.
We aim to make studying easier for students by giving them the right materials to prepare for exams.
NEB Class 12 Physics Fluid statics Note Handwritten in PDF
Fluid statics and dynamics is one of the most application-rich chapters in Class 12 Physics. It explains phenomena from why ships float to how airplanes fly. The chapter has 9 topics in the NEB syllabus and frequently appears as both theory and numerical questions in board exams.
Pressure in Fluids and Pascal’s Law
Pressure at depth h in a fluid: P = Pβ + Οgh
- Pressure increases with depth
- Pressure at same depth is equal in all directions (Pascal’s law)
Pascal’s Law: Pressure applied to an enclosed fluid is transmitted equally and undiminished in all directions throughout the fluid.
Applications:
- Hydraulic press (small force β large force through area multiplication)
- Hydraulic brakes in vehicles
- Hydraulic lift at car service stations
Archimedes’ Principle and Floatation
Archimedes’ Principle: A body partially or fully immersed in a fluid experiences an upward buoyant force equal to the weight of fluid displaced.
F_buoyancy = Ο_fluid Γ V_displaced Γ g
Law of Floatation: A floating body displaces fluid whose weight equals the total weight of the body.
- If density of object < density of fluid β floats
- If density of object > density of fluid β sinks
- Steel ships float because their average density (including hollow interior) is less than water
Important terms:
- Upthrust = buoyant force (acts upward)
- Center of buoyancy = centroid of displaced fluid volume
- Metacenter = point through which upthrust acts when tilted (important for ship stability)
Surface Tension
Surface tension exists because molecules at the surface of a liquid have a net inward force (unlike interior molecules, which are pulled equally in all directions). The surface behaves like a stretched elastic membrane.
- Definition: Force per unit length along the surface = T = F/L (N/m)
- Alternatively: Surface energy per unit area = T = W/A (J/mΒ²)
Excess pressure inside curved surfaces:
- Inside a liquid drop: ΞP = 2T/r
- Inside a soap bubble: ΞP = 4T/r (two surfaces)
- Inside an air bubble in liquid: ΞP = 2T/r
Angle of contact (ΞΈ):
- ΞΈ < 90Β° β liquid wets the surface (water on glass, ΞΈ β 0Β°)
- ΞΈ > 90Β° β liquid does not wet (mercury on glass, ΞΈ β 135Β°)
Capillarity
Capillarity is the rise or fall of a liquid in a narrow tube due to surface tension.
Rise formula: h = 2T cosΞΈ / (Οgr)
- Water rises in a glass capillary (cohesion < adhesion, ΞΈ < 90Β°)
- Mercury falls in a glass capillary (cohesion > adhesion, ΞΈ > 90Β°)
- Narrower tube β greater rise
- Applications: water rise in tree roots, oil rise in lamp wick, ink in pen
Viscosity and Newton’s Formula
Viscosity is the internal friction of a fluid β resistance to flow.
Newton’s formula: F = Ξ·A(dv/dy)
Where:
- Ξ· = coefficient of viscosity (PaΒ·s or NΒ·s/mΒ²)
- dv/dy = velocity gradient (rate of change of velocity with distance)
Laminar vs Turbulent flow:
- Laminar flow: Smooth, layered, low velocity (Re < 2000)
- Turbulent flow: Chaotic, high velocity (Re > 4000)
- Reynolds number: Re = ΟvD/Ξ· (dimensionless β predicts flow type)
Poiseuille’s Formula
Rate of flow of viscous fluid through a pipe:
Q = ΟPrβ΄ / 8Ξ·l
Key insight: Flow rate depends on rβ΄ β doubling the pipe radius increases flow by 16 times. This is why even partial blockage of an artery (reduced r) dramatically reduces blood flow β critical in cardiovascular medicine.
Stokes Law and Terminal Velocity
Stokes Law: Viscous drag force on a sphere = F = 6ΟΞ·rv
At terminal velocity, drag + upthrust = weight:
Terminal velocity: v_t = 2rΒ²(Ο β Ο)g / 9Ξ·
Where Ο = sphere density, Ο = fluid density
This formula is used to experimentally measure the coefficient of viscosity by dropping small spheres through a fluid and measuring their terminal velocity.
Equation of Continuity and Bernoulli’s Equation
Equation of continuity (for incompressible fluid): Aβvβ = Aβvβ
Fluid speeds up in narrower sections β explains why river water flows faster in a narrow gorge.
Bernoulli’s Equation: P + Β½ΟvΒ² + Οgh = constant
This means total energy per unit volume (pressure energy + kinetic energy + potential energy) is conserved along a streamline.
Applications:
- Airplane wing lift (curved top β faster air β lower pressure β upward lift)
- Venturi meter (measures fluid flow speed)
- Spray gun, atomizer, carburetor
- Why a ball curves in cricket/football (Magnus effect)
Class 12 Science Faculty All Subject Notes
- Physics Handwritten Notes PDF
- Chemistry Handwritten Notes PDF
- Biology Handwritten Notes PDF
- Nepali Handwritten Notes PDF
- English Handwritten Notes PDF
Student Queries:- Class 12 Physics Notes download | Complete Physics Guide (New Syllabus) | Class 12 Physics Book Solution Guide App | Class 12 Physics Book Notes 2081 Guide | Class 12 Physics All Chapter Notes | Kec Publication Physics class 12 solutions | Neb class 12 physics notes pdf free download | Neb class 11 physics notes handwritten | Class 12 Physics Notes PDF | NEB Class 12 Physics Book PDF | Principle of Physics Class 12 pdf Asmita publication | NEB Class 12 Physics syllabus 2080 | Class 12 Physics Book PDF Nepal 2080
NOTE : βIf you want to download the notes Offline Contact us in Social media β
Frequently Asked Questions
What is Bernoulli’s equation in Class 12 Physics?
Bernoulli’s equation: P + Β½ΟvΒ² + Οgh = constant along a streamline. Total energy per unit volume β pressure, kinetic, and potential β is conserved for ideal fluid flow. Applications include airplane lift, Venturi meter, spray guns, and why roofs blow off during strong storms.
What is Stokes law and terminal velocity in Class 12?
Stokes law: drag force on sphere = 6ΟΞ·rv. At terminal velocity drag + upthrust = weight, giving v_t = 2rΒ²(ΟβΟ)g/9Ξ·. Terminal velocity increases with larger radius and density difference. This formula is used experimentally to measure the coefficient of viscosity of a liquid.
What is Pascal’s law with application Class 12?
Pascal’s law: pressure applied to enclosed fluid transmits equally in all directions. In a hydraulic press Fβ/Fβ = Aβ/Aβ β small force on small piston creates large force on large piston. Applications include hydraulic brakes, hydraulic lift, and hydraulic jacks used in vehicle service stations.
What is surface tension and excess pressure in Class 12?
Surface tension T = force per unit length (N/m) = surface energy per unit area. Excess pressure inside a soap bubble = 4T/r (two surfaces). Inside a liquid drop = 2T/r (one surface). Inside an air bubble in liquid = 2T/r. These formulas appear regularly in NEB board exams.
What is capillarity formula in Class 12 Physics?
Capillarity formula: h = 2T cosΞΈ/(Οgr). Water rises in glass capillary because angle of contact is less than 90Β° (adhesion greater than cohesion). Mercury falls in glass because angle of contact exceeds 90Β°. Narrower tube gives greater capillary rise. Used to explain water rise in plant roots.
What is the equation of continuity in fluid dynamics?
Equation of continuity: Aβvβ = Aβvβ. For incompressible fluid in steady flow, area times velocity is constant throughout. Fluid speeds up through narrower sections. This explains why river water flows faster in narrow gorges and why squeezing a hosepipe end increases water speed significantly.
What is Reynolds number in Class 12 Physics?
Reynolds number Re = ΟvD/Ξ· predicts flow type. Re below 2000 means laminar flow (smooth and layered). Re above 4000 means turbulent flow (chaotic). It depends on density, velocity, pipe diameter, and viscosity. Engineers use it to design pipelines, aircraft surfaces, and blood vessel medical models.
Which Fluid Statics topics are most important for NEB 2083?
Most important: Bernoulli’s equation with applications (4 marks), Stokes law terminal velocity derivation (4 marks), surface tension excess pressure formulas (2 marks), capillarity (2 marks), and Pascal’s law numericals. Bernoulli and Stokes law numericals appear in almost every NEB Class 12 board paper.
