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General Knowledge

CDS · NDA · AFCAT · Indian Army / Navy / Air Force Exams

1

Physics

Laws of Motion (Newton)

Three Laws

  • 1st Law (Inertia): A body at rest/motion continues so unless acted upon by external force
  • 2nd Law (F = ma): Force = mass × acceleration
  • 3rd Law (Action-Reaction): Every action has an equal and opposite reaction

Work, Energy & Power

Formulas

  • Work (W) = F × d × cos θ (Joules)
  • Kinetic Energy = ½mv² ; Potential Energy = mgh
  • Power (P) = W/t (Watts); 1 horsepower = 746 W
  • Law of Conservation of Energy: KE + PE = constant (in closed system)

Heat & Thermodynamics

Key Concepts

  • Heat flows from higher to lower temperature (zeroth law)
  • 1st Law: ΔU = Q − W (energy conservation)
  • 2nd Law: Heat cannot spontaneously flow from cold to hot body
  • Specific heat of water: 4200 J/kg·K (highest of common substances)
  • Latent heat: heat absorbed/released during phase change (no temperature change)

Optics

Mirror & Lens Formulas

  • Mirror equation: 1/f = 1/v + 1/u
  • Lens formula: 1/f = 1/v − 1/u
  • Magnification m = −v/u (mirror); m = v/u (lens)
  • Speed of light: 3 × 10⁸ m/s in vacuum
  • Total internal reflection: basis of optical fibre; occurs when angle > critical angle

⚔️ Defence GK Physics Focus

Sound waves in seawater (SONAR), electromagnetic spectrum (RADAR uses microwave), supersonic/hypersonic aircraft speeds (Mach number), nuclear fission (Atom bomb) vs fusion (H-bomb). These directly link physics to defence technology.

2

Chemistry

Periodic Table Basics

Key Facts

  • 118 elements; 7 periods, 18 groups
  • Metals (left side): good conductors; Nonmetals (right): poor conductors
  • Noble gases (Group 18): He, Ne, Ar, Kr, Xe, Rn — inert
  • Alkali metals (Group 1): highly reactive; stored in kerosene (Na, K)
  • Transition metals (Groups 3–12): variable oxidation states

Acids, Bases & Salts

SubstancepHExample
Strong Acid0–3HCl, H₂SO₄, HNO₃
Weak Acid3–6CH₃COOH (vinegar), H₂CO₃
Neutral7Pure water
Weak Base8–10NH₃ (ammonia)
Strong Base11–14NaOH, KOH

Important Compounds & Uses

CompoundFormulaCommon Use
Baking SodaNaHCO₃Antacid, baking
Common SaltNaClFood preservation
Bleaching PowderCa(OCl)ClDisinfectant, water treatment
Plaster of ParisCaSO₄·½H₂OFracture cast, statues
TNTC₇H₅N₃O₆Explosive
RDXC₃H₆N₆O₆Military explosive

⚔️ Defence Chemistry

RDX, C-4, Semtex are plastic explosives. Napalm = incendiary gel. Propellants in rockets: liquid H₂ + liquid O₂ (cryogenic). Chemical weapons (Sarin, VX) are nerve agents — CWC 1993 bans them.

3

Biology

Human Body Systems

SystemKey OrgansFunction
CirculatoryHeart, blood vesselsPumps oxygenated blood; 72 beats/min normal heart rate
RespiratoryLungs, diaphragmGas exchange (O₂ in, CO₂ out); 16–18 breaths/min
DigestiveStomach, small intestineEnzyme breakdown & nutrient absorption
NervousBrain, spinal cord, nervesCoordinates all body functions
EndocrinePituitary, thyroid, adrenalHormone regulation
Skeletal206 bones (adult)Support, movement, protection

Nutrition & Vitamins

VitaminDeficiency DiseaseSource
ANight blindnessCarrots, liver
B1 (Thiamine)BeriberiCereals, legumes
B12Pernicious anaemiaMeat, dairy
CScurvyCitrus fruits
DRickets (children)Sunlight, fish oil
KBlood clotting failureGreen leafy vegetables

💡 Medical Standards for Defence

NDA/CDS require minimum height (162.5 cm men, 152 cm women), weight in proportion, normal BP (120/80 mmHg), vision standards, and no flat feet. Understand the biological basis of each criterion.

4

Indian History

Major Indian Battles

BattleYearOutcome
1st Battle of Panipat1526Babur defeats Ibrahim Lodi → Mughal Empire begins
2nd Battle of Panipat1556Akbar (Bairam Khan) defeats Hemu → Mughal consolidation
3rd Battle of Panipat1761Ahmad Shah Abdali defeats Marathas
Battle of Plassey1757British (Clive) defeat Siraj ud-Daulah → British rule begins
Battle of Buxar1764British defeat combined Mughal-Nawab force → consolidated control
Anglo-Mysore Wars (4)1767–17994th war: Tipu Sultan killed; British annex Mysore

Independence Movement

Key Events

  • 1857 — First War of Independence (Sepoy Mutiny); centres: Meerut, Delhi, Kanpur
  • 1885 — Indian National Congress founded by A.O. Hume
  • 1919 — Jallianwala Bagh Massacre; Rowlatt Act
  • 1920–22 — Non-Cooperation Movement (Gandhi)
  • 1930 — Civil Disobedience / Salt March (Dandi, 241 miles)
  • 1942 — Quit India Movement; "Do or Die"
  • 1947 — Independence; Partition; Aug 14/15
5

Indian Polity

Constitution Basics

Key Facts

  • Adopted: 26 Nov 1949; Effective: 26 Jan 1950
  • Originally: 395 Articles, 8 Schedules, 22 Parts
  • Currently: ~470 Articles, 12 Schedules, 25 Parts, 106 Amendments
  • Preamble: Sovereign, Socialist, Secular, Democratic, Republic (SSSDR)
  • World's longest written constitution

Defence-Related Constitutional Provisions

President as Supreme Commander

  • Article 53: Supreme command of defence forces vests in the President
  • Article 352: National Emergency (armed rebellion / external aggression)
  • Article 355: Union's duty to protect states from external aggression and internal disturbance
  • Article 356: President's Rule in states
  • AFSPA (Armed Forces Special Powers Act): operational in certain states
6

Geography

India's Strategic Geography

Important Passes (Military Significance)

PassStateConnects / Significance
Nathu LaSikkimIndia–China; opened 2006 after 1962 war closure
Zoji LaJ&K / LadakhConnects Srinagar to Leh; strategic NH-1
Khardung LaLadakhHighest motorable road; strategic for Siachen
BanihalJ&KJammu–Srinagar; Jawahar Tunnel
RohtangHimachal PradeshManali to Lahaul-Spiti; Atal Tunnel built (2020)

Important Islands & Borders

EntityKey Facts
Andaman & NicobarBay of Bengal; southern-most point: Indira Point; naval base INS Baaz
LakshadweepArabian Sea; coral islands; naval base INS Divyashakti
Line of Actual Control (LAC)De facto India–China border; 3,488 km (disputed)
Line of Control (LoC)India–Pakistan in J&K; drawn after 1971 war; Simla Agreement 1972
Sir CreekDisputed maritime boundary between India and Pakistan in Rann of Kutch
7

Defence GK — Ranks, Awards & Exercises

Ranks of Indian Armed Forces

ArmyNavyAir Force
Field Marshal (honorary)Admiral of the Fleet (honorary)Marshal of IAF (honorary)
GeneralAdmiralAir Chief Marshal
Lieutenant GeneralVice AdmiralAir Marshal
Major GeneralRear AdmiralAir Vice Marshal
BrigadierCommodoreAir Commodore
ColonelCaptainGroup Captain
Lieutenant ColonelCommanderWing Commander
MajorLieutenant CommanderSquadron Leader
CaptainLieutenantFlight Lieutenant
LieutenantSub-LieutenantFlying Officer

Gallantry Awards

AwardRankDescription
Param Vir Chakra (PVC)HighestMost conspicuous bravery in the presence of enemy; 21 recipients
Maha Vir Chakra (MVC)2nd highestActs of conspicuous gallantry in the presence of enemy
Vir Chakra (VrC)3rdActs of gallantry in the presence of enemy
Ashoka ChakraPeacetime highestGallantry, courage, self-sacrifice away from battlefield
Kirti ChakraPeacetime 2ndOutstanding acts of gallantry, courage away from battlefield
Shaurya ChakraPeacetime 3rdGallantry away from the battlefield

Major Joint Military Exercises

ExerciseCountriesType
Yudh AbhyasIndia–USAArmy (joint training)
MalabarIndia–USA–Japan (+ Australia)Naval
ShaktiIndia–FranceArmy
GarudaIndia–FranceAir Force
Tasman SaberIndia–AustraliaNaval
Hand-in-HandIndia–ChinaArmy (counter-terrorism)
IndraIndia–RussiaTri-service (Army/Navy/Air)
SLINEXIndia–Sri LankaNaval
Surya KiranIndia–NepalArmy
EKUVERINIndia–MaldivesArmy

Key Defence Organisations & Weapons

DRDO & Indigenous Weapons

  • DRDO: Defence Research & Development Organisation; HQ New Delhi
  • Agni missiles: Agni-I (700 km) to Agni-V (5000+ km, ICBM range)
  • Prithvi: Short-range surface-to-surface ballistic missile
  • BrahMos: Indo-Russian supersonic cruise missile; fastest in the world; range ~290 km
  • Arjun MBT: Main Battle Tank; made by DRDO/HVF, Chennai
  • Tejas: Light Combat Aircraft (LCA); indigenously developed by HAL
  • INS Vikrant: India's first domestically built aircraft carrier (2022)

⚔️ Key Defence Headquarters

  • Indian Army HQ: South Block, New Delhi
  • Indian Navy HQ: Integrated HQ, New Delhi
  • Indian Air Force HQ: Vayu Bhavan, New Delhi
  • Chief of Defence Staff (CDS): Head of Dept of Military Affairs; created 2019
  • NDA: National Defence Academy, Khadakwasla, Pune
  • IMA: Indian Military Academy, Dehradun
  • OTA: Officers Training Academy, Chennai & Gaya
  • Indian Naval Academy: Ezhimala, Kerala
  • Air Force Academy: Dundigal, Hyderabad

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