9th Class Physics Notes — All Chapters (Punjab, Federal, KPK Board 2026)

These 9th class physics notes cover all nine chapters of the Punjab Board, Federal Board, and KPK Board syllabus. Each chapter includes key definitions, important formulas, short question answers, and solved numerical problems — everything you need for board exam revision.

Chapter 1: Physical Quantities and Measurement — Key Notes

Definitions to memorise:

• Physical quantity: A measurable quantity (e.g., length, mass, time)
• Base quantities: Seven fundamental quantities — length (m), mass (kg), time (s), temperature (K), electric current (A), luminous intensity (cd), amount of substance (mol)
• Derived quantities: Quantities derived from base quantities (e.g., speed = distance/time, m/s)
• Significant figures: All accurately known digits plus the first doubtful digit
• Least count: The smallest reading a measuring instrument can measure

Key formulas: Least count of vernier callipers = smallest main scale division ÷ number of vernier divisions. Least count of screw gauge = pitch ÷ number of circular scale divisions.

Chapter 2: Kinematics — Key Notes

Definitions:

• Displacement: Shortest distance between two points (vector quantity)
• Velocity: Rate of change of displacement (vector); Speed: rate of change of distance (scalar)
• Acceleration: Rate of change of velocity (a = Δv/Δt)

Equations of motion:

• v = v₀ + at
• s = v₀t + ½at²
• v² = v₀² + 2as

Board tip: For freely falling bodies, replace a with g (9.8 m/s²) and for upward motion, use g as negative.

Chapter 3: Dynamics — Key Notes

Newton's Laws:

• First Law (Inertia): A body remains at rest or in uniform motion unless acted upon by an external force
• Second Law: F = ma (force equals mass times acceleration)
• Third Law: Every action has an equal and opposite reaction

Key formulas: Momentum p = mv. Impulse = FΔt = Δp. Weight W = mg. Friction force f = μN.

Chapter 4: Turning Effect of Forces — Key Notes

• Torque (τ): τ = F × d (force × perpendicular distance from pivot)
• Principle of moments: For equilibrium, sum of clockwise moments = sum of anticlockwise moments
• Couple: Two equal and opposite parallel forces acting on a body
• Conditions of equilibrium: (1) ΣF = 0, (2) Στ = 0

Chapter 5: Gravitation — Key Notes

• Law of gravitation: F = Gm₁m₂/r² where G = 6.674 × 10⁻¹¹ Nm²/kg²
• Gravitational field strength: g = Gm/r² (at Earth's surface, g ≈ 9.8 m/s²)
• Mass vs weight: Mass is constant everywhere; weight (W = mg) changes with location
• Orbital velocity: v = √(gR) for a satellite near Earth's surface

Chapter 6: Work and Energy — Key Notes

• Work: W = Fd cos θ (SI unit: joule)
• Kinetic energy: KE = ½mv²
• Potential energy: PE = mgh
• Power: P = W/t (SI unit: watt)
• Efficiency: η = (useful output / total input) × 100%
• Law of conservation of energy: Energy cannot be created or destroyed, only converted from one form to another

Chapter 7: Properties of Matter — Key Notes

• Pressure: P = F/A (SI unit: pascal, Pa)
• Liquid pressure: P = ρgh (increases with depth)
• Pascal's law: Pressure applied to an enclosed fluid is transmitted equally in all directions
• Archimedes' principle: Upthrust on a body = weight of fluid displaced
• Hooke's law: F = kx (within elastic limit, extension is proportional to force)
• Stress = Force/Area; Strain = Change in length/Original length; Young's modulus = Stress/Strain

Chapter 8: Thermal Properties of Matter — Key Notes

• Heat equation: Q = mcΔT (Q = heat, m = mass, c = specific heat, ΔT = temperature change)
• Latent heat of fusion: Qf = mLf (heat to change solid→liquid at constant temperature)
• Latent heat of vaporisation: Qv = mLv (heat to change liquid→gas at constant temperature)
• Linear expansion: ΔL = αLΔT
• Volume expansion: ΔV = βVΔT where β ≈ 3α

Chapter 9: Transfer of Heat — Key Notes

• Conduction: Heat transfer through a material without movement of the material itself (metals are good conductors)
• Convection: Heat transfer through fluid movement (e.g., land and sea breezes)
• Radiation: Heat transfer through electromagnetic waves — no medium needed
• Thermos flask: Uses vacuum (prevents conduction and convection), silvered walls (prevents radiation)

How to Use These Notes for Exam Preparation

These notes are a revision summary, not a replacement for your textbook. Use them as follows:

• Read the textbook chapter first for full understanding
• Use these notes for quick revision before exams
• Test yourself: cover the formulas and try to recall them from memory
• Practice MCQs on HighYield after revising each chapter to test application