General Physics & Everyday Chemistry
🎯 PYQs — Physics & Chemistry (Moderate Frequency)
Most Asked Topics:
- Newton's Laws applications
- Pressure and altitude effects
- Doppler Effect
- TIR and optical fibers
- Plastics types
Common Traps:
- ❌ Speed of sound higher in solids (not gases)
- ❌ Centrifugal force is apparent/pseudo (not real)
- ❌ Water is densest at 4°C (not 0°C)
1. Mechanics
Scalar vs Vector Quantities
| Distinguish between Scalar and Vector quantities with examples. | - Scalar Quantities: Magnitude only. Examples: Distance, Speed, Mass, Time. Vector Quantities: Magnitude + Direction. Examples: Displacement, Velocity, Force, Acceleration. |
Key Kinematic Terms
| Define Velocity, Acceleration, Momentum, Force, and the Law of Conservation of Momentum. | - Velocity ($v$): Rate of change of displacement ($v = \Delta s/\Delta t$; m/s). - Acceleration ($a$): Rate of change of velocity ($a = \Delta v/\Delta t$; m/s²). - Momentum ($P$): Mass $\times$ Velocity ($P = mv$; kg·m/s). - Force ($F$): Push or pull causing acceleration ($F = ma$; Newton). Law of Conservation of Momentum: Total momentum remains constant in an isolated system (no external force) (e.g., escaping a frozen lake by throwing a bag in the opposite direction). |
Newton's Laws of Motion
| State Newton's three laws of motion with everyday applications. | -
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Friction & Contact Mechanics
| Explain factors causing friction, contact mechanics, friction types, and methods to reduce friction. | Friction Factors: Microscopic surface irregularities, molecular adhesion, normal load, and material properties. Contact Mechanics: - Real Contact Area: True microscopic touching area (much smaller than apparent area). - Apparent Contact Area: Macroscopic visible touching region. Types of Friction:
Friction Control:
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Circular Motion & Centrifugal Force
| Distinguish centripetal and centrifugal forces and list their applications. | - Centripetal Force: Real force directed toward the center of a circular path ($F = mv^2/r$). Centrifugal Force: Apparent outward force arising from inertia (a pseudo/apparent force, not real). Applications: Cream separation (skimming milk), banking of curved roads, Earth's oblate shape, laboratory centrifuges, and ocean tides (in conjunction with gravity). |
Airplane Lift
| How does Bernoulli's Principle explain airplane lift? | - Airplane Lift: Airplane lift exploits pressure differences. Faster air flow over the curved top surface creates low pressure (suction), while the bottom surface maintains higher pressure, generating upward lift force (Bernoulli's principle). |
2. Advanced Sensors & Energy Harvesting
Energy Harvesting
| Define energy harvesting, its ambient sources, and applications. | Energy Harvesting: Capturing ambient energy (light, heat, vibration) to generate usable electricity. Sources: - Thermoelectric: Uses waste heat via Seebeck effect. - Piezoelectric: Uses mechanical vibrations or human motion (e.g., smart floors/shoes). - Triboelectric Nanogenerators (TENGs): Converts low-frequency mechanical energy into electricity via contact electrification. Applications: IoT sensors, wearables, medical implants, smart building tech. |
Modern Sensing Technologies
| Detail MEMS sensors, accelerometer uses, nano-sensors, and vibration/acoustic sensors. | - MEMS (Micro-Electrical-Mechanical Systems): Micro-scale machines on a chip. Accelerometer Applications: Deploying airbags in car crashes, rotating smartphone displays, and turning off hard drives during accidental falls. Nano-sensors: Vast surface-area-to-volume ratio for targeted pathogen detection and precision agriculture. Acoustic Sensors: Bridge monitoring and early earthquake warning systems (detecting P-waves). |
3. Pressure
Pressure Basics
| State the pressure formula, SI unit, and factors affecting pressure. | - Pressure Formula: $P = F/A$ (Force per unit area). SI Unit: Pascal (Pa) = 1 N/m² ($1 \text{ atm} = 1.013 \times 10^5 \text{ Pa}$). Factors: Directly proportional to force and density of fluid; increases with depth in liquids; inversely proportional to area of contact. |
Pressure Applications
| Outline everyday applications of pressure differences. | Applications: - Straw drinking: Low pressure inside straw; atmospheric pressure pushes liquid up. - Hydraulic lifts: Small force on small piston → Large force on large piston. - Land/Sea Breeze: Differential heating creates pressure differences. - Cloud formation: Low pressure → Rising air → Cooling → Condensation. |
Pressure & Altitude
| How do pressure and altitude interact? Explain boiling point changes and pressure cooker mechanics. | - Altitude Interaction: Atmospheric pressure decreases with altitude because there is less air column above. Boiling Point: Decreases at higher altitudes ($<100^\circ\text{C}$ on mountain tops). Pressure Cooker: Increases internal pressure, raising the water's boiling point, which cooks food faster. The temperature reached depends mainly on the area of the lid hole and the weight of the lid. |
4. Fluid Dynamics
Flow Types
| Compare Laminar and Turbulent fluid flow. | - Laminar Flow: Smooth, parallel layers of fluid; low Reynolds number (e.g., blood flow in capillaries). Turbulent Flow: Chaotic, mixing fluid flow; high Reynolds number (e.g., river rapids). |
Diffusion, Osmosis, Dialysis
| Distinguish between Diffusion, Osmosis, and Dialysis. | Physical Transport Mechanisms: - Diffusion: Net movement of particles from high to low concentration (e.g., oxygen diffusing into blood in lungs). - Osmosis: Movement of water molecules through a semipermeable membrane from low solute to high solute concentration (e.g., plant root absorption). - Dialysis: Selective movement of solutes based on particle size across a semipermeable membrane (e.g., kidney dialysis). |
Surface Tension & Capillarity
| Explain surface tension, capillarity, concave vs convex menisci, anomalous density of water, and wettability. | - Surface Tension: Liquid surface behaves like a stretched elastic membrane due to cohesive forces. Capillarity: Rise or fall of liquid in narrow tubes. Concise: Concave meniscus (e.g., water) rises because Adhesion > Cohesion; Convex meniscus (e.g., mercury) falls because Cohesion > Adhesion (e.g., kerosene lamp wicks, water transport in xylem). Anomalous Density: Water reaches maximum density at 4°C. Ice floats, insulating liquid water underneath and preserving aquatic life. Wettability: Depends on solid surface energy vs liquid surface tension. Hydrophilic surfaces spread water, hydrophobic surfaces form droplets (lotus-effect). Nano-Water Treatment: Iron oxide nanoparticles remove heavy metals; silver nanoparticles kill microbes; nano-bubbles prevent algal growth. |
5. Heat & Thermodynamics
Temperature vs Heat
| Compare Temperature and Heat: definitions, units, and thermodynamic nature. | - Temperature: Measure of average kinetic energy of molecules; intensive property (independent of amount); units in Kelvin (K) or Celsius (°C). Heat: Energy transferred due to a temperature difference; extensive property (depends on amount); units in Joules (J). |
Specific Heat Capacity
| Define specific heat capacity and explain the ecological/biological importance of water's high specific heat. | - Specific Heat Capacity: Heat required to raise the temperature of 1 kg of a substance by 1°C. Water's High Specific Heat: Moderates global climate by storing/releasing heat slowly, keeps coastal regions warmer in winter, and acts as a thermal shield to stabilize human body temperature. |
Special Properties of Water
| List the special thermal properties of water and define latent heat. | - Water's Key Properties: Maximum density at 4°C, ice floating, and high latent heat. Latent Heat: Heat energy absorbed or released during a phase change without changing the temperature (e.g., latent heat of fusion and latent heat of vaporization). |
Heat Transfer & Radiative Cooling
| Detail the three modes of heat transfer, black body radiation, passive radiative cooling, and nano-thermal physics. | - Heat Transfer: Conduction (direct contact), Convection (fluid movement like motor car radiators), and Radiation (no medium needed). Black Body Radiation: Ideal emitter/absorber; peak wavelength shifts to shorter wavelengths as temperature rises. Radiative Cooling: Passive cooling where surfaces emit heat as infrared radiation to outer space (e.g., white-painted roofs). Nano-Scale Heat: Conducted via phonons. Heat sinks use graphene or carbon nanotubes (CNTs) for fast dissipation in microcircuits. |
Cryogenics
| Define cryogenics and list its major applications. | - Cryogenics: Study of materials at extremely low temperatures (below -150°C). Applications: Liquid hydrogen/oxygen rocket propellants, cooling MRI superconducting magnets, cryopreservation of biological tissues, LNG transport, and cryosurgery. |
6. Optics & EM Radiation
Electromagnetic (EM) Spectrum
| Order the EM spectrum by energy, and detail visible light, IR, and UV properties. | - EM Spectrum Order (Lowest to Highest Energy): Radio → Microwave → Infrared → Visible (Red to Violet) → Ultraviolet (UV) → X-rays → Gamma rays. Infrared (IR): Emitted by hot bodies; used in night vision, remote controls, and motion sensors. Ultraviolet (UV): UVA (deep skin penetration), UVB (sunburn/DNA damage), UVC (most energetic, ozone-absorbed). UV radiation inactivates microorganisms in water purification but does not remove odour/turbidity. Albedo: High albedo reflects radiation (cooling), low albedo absorbs radiation (warming). |
Lighting Technologies
| Compare Sodium Vapour, LED, OLED, and QLED lighting technologies. | Lighting Framework: - Sodium Vapour: Omnidirectional, yellow monochromatic light; high efficiency, poor color rendering. - LED: Directional light via electron-hole recombination; broad-spectrum, long life. - OLED: Self-emissive organic materials (no backlight needed); can be made flexible/transparent. - QLED: Inorganic quantum dots with LED backlight; brighter and longer lasting than OLED, lower color accuracy. |
Reflection
| State the laws of reflection and their applications. | - Laws of Reflection: Angle of incidence equals angle of reflection; incident, reflected, and normal rays lie in the same plane. Applications: Flat/curved mirrors, solar cookers, periscopes. |
Refraction
| Explain refraction, refractive index, and lens corrections. | Refraction: Bending of light when crossing mediums of different optical densities (denser slows/bends toward normal, rarer speeds/bends away). Refractive Index ($n$): $n = c/v$ (speed of light in vacuum vs medium). Lenses: - Convex: Converging lens; corrects hyperopia (farsightedness). - Concave: Diverging lens; corrects myopia (nearsightedness). |
Total Internal Reflection (TIR)
| Define Total Internal Reflection (TIR) and list its applications. | - TIR: Occurs when light travels from a denser to a rarer medium and the angle of incidence exceeds the critical angle. Applications: Optical fiber communications, diamond brilliance, and mirages. |
Dispersion
| What is dispersion? Explain VIBGYOR and rainbow formation. | - Dispersion: Splitting of white light into its component colors by a prism. Wavelengths (VIBGYOR): Violet bends the most (shortest wavelength), Red bends the least (longest wavelength). Rainbow: Combined effect of dispersion, refraction, and internal reflection in water droplets. |
Doppler Effect
| Define the Doppler Effect and outline its applications in astronomy and technology. | - Doppler Effect: Change in frequency of a wave relative to an observer who is moving relative to the wave source (approaching has higher pitch/frequency; receding has lower). Applications: Redshift/blueshift in astrophysics, Doppler ultrasound, radar speed detection guns. |
7. Sound
Sound Basics
| Detail sound properties: wave nature, speed in different phases, and human hearing range. | - Sound Waves: Longitudinal mechanical waves; require a medium (cannot travel in vacuum). Speed of Sound: Solids > Liquids > Gases (speed in air $\approx$ 343 m/s). Hearing Range: 20 Hz to 20,000 Hz for healthy humans. |
Key Sound Terms
| Define Hypersonic speed, Mach Number, Sonic Boom, Ultrasound, and Infrasound. | Sound Properties: - Hypersonic: Speeds exceeding Mach 5 (5 times the speed of sound). - Mach Number: Ratio of object speed to the speed of sound in the surrounding medium. - Sonic Boom: Shock waves created when an object travels faster than sound. - Ultrasound: Frequencies above 20,000 Hz (used in medical scans, SONAR). - Infrasound: Frequencies below 20 Hz (e.g., earthquakes, elephant communication). |
Sound Applications
| List applications of SONAR, medical ultrasound, and acoustic levitation. | Applications: - SONAR: Sound Navigation and Ranging used by submarines to map/detect underwater objects. - Medical Scan: High-frequency sound waves image soft tissues without radiation. - Acoustic Levitation: Using intense sound waves to counteract gravity and levitate small objects. |
8. Electricity & Magnetism
Basic Electrical Concepts
| Define electric charge, current, voltage, resistance, and Ohm's Law. | Electrical Terms: - Charge ($Q$): Physical property of matter causing EM force (Coulomb). - Current ($I$): Rate of flow of charge (Ampere). - Voltage ($V$): Electric potential difference (Volt). - Resistance ($R$): Opposition to current flow (Ohm). Ohm's Law: $V = I \times R$. |
Circuit Types
| Compare Series and Parallel circuits and explain home wiring. | - Series Circuits: Same current through all components; voltage divides. Parallel Circuits: Same voltage across all components; current divides. Home Wiring: Always connected in parallel so appliances can operate independently at the same voltage. |
Magnetism & Electromagnetism
| Define magnetic fields, electromagnetism, Faraday's Law, and list applications. | - Concepts: Moving charges produce magnetic fields (Tesla), and changing magnetic flux induces electromotive force (Faraday's Law). Applications: Electric motors, generators, transformers, MRI machines, and Maglev trains. |
Natural Phenomena
| Explain Auroras and Lightning. | - Aurora: Solar charged particles interacting with Earth's magnetic field near polar regions. Lightning: High-voltage electrical discharge between cloud layers or clouds and the ground. |
9. Particle & Astroparticle Physics
Standard Model & Fundamental Particles
| Recall quarks, leptons, force-carrying bosons, and the limits of the Standard Model. | - Fermions: Quarks (building blocks of hadrons like protons/neutrons) and Leptons (electrons, neutrinos). Bosons: Gluons (strong force carrier) and Higgs Boson (gives mass to particles). Incompleteness: Standard Model does not account for Gravity, Dark Matter, or Matter-Antimatter asymmetry. |
Fundamental Forces of Nature
| Name and compare the four fundamental forces of nature: carriers, ranges, and strengths. | Forces Comparison: - Strong Nuclear: Binds protons/neutrons in nucleus; strongest force; subatomic range; carrier: Gluons. - Electromagnetic: Acts on charged particles; infinite range; carrier: Photons. - Weak Nuclear: Causes radioactive beta decay; subatomic range (shortest); carrier: W, Z bosons. - Gravitational: Universal mass attraction; weakest force; infinite range; carrier: Graviton (theoretical). |
Neutrinos & Observatories
| Detail neutrinos, neutrino oscillations, Cherenkov radiation, and the INO project. | - Neutrinos: Massless/nearly massless ghost particles interacting only via weak nuclear force and gravity. Change flavor (oscillate) during travel, proving they have mass. Cherenkov Radiation: Blue light emitted when charged particles exceed the phase velocity of light in a medium. Observatories: IceCube (Antarctica), Super-Kamiokande (Japan), and the proposed India-based Neutrino Observatory (INO) at Theni, TN (Iron Calorimeter detector). |
CERN & Large Hadron Collider
| Detail the Large Hadron Collider (LHC) and its primary detector experiments. | - LHC: World's largest particle accelerator (27-km ring) at CERN, Geneva. Experiments: ATLAS & CMS (discovered Higgs), ALICE (heavy ions), LHCb (matter-antimatter), CLOUD (cosmic rays/climate). |
10. Chemistry in Everyday Life
Medicines & Drugs
Drug Classification
| Classify common medicines: Analgesics, Antipyretics, Antibiotics, Antacids, Antihistamines, and Tranquilizers. | Pharmaceutical Database: - Analgesics: Pain relief (Aspirin, Ibuprofen, Morphine). - Antipyretics: Fever reduction (Paracetamol). - Antibiotics: Kill bacteria (Penicillin, Azithromycin). - Antacids: Neutralize stomach acid (Magnesium hydroxide, Omeprazole). - Antihistamines: Block histamine in allergies (Cetirizine, Fexofenadine). - Tranquilizers: Anxiety/tension reduction (Alprazolam, Clonazepam). |
Chemicals in Food
Food Additives
| Outline food additives: Preservatives, Artificial Sweeteners, and Antioxidants. | Food Chemistry: - Preservatives: Prevent spoilage (Sodium benzoate, Potassium sorbate). - Artificial Sweeteners: Low-calorie sweets (Aspartame - 100x sweeter than sugar, Sucralose, Stevia). - Antioxidants: Prevent food oxidation (BHA, BHT). |
Chemicals of Concern
| Explain health concerns of Aspartame, Titanium Dioxide, BPA, and Triclosan. | Concern Database: - Aspartame: Diet foods; metabolized providing calories but used in minute amounts. - Titanium Dioxide: Candies, toothpaste; nanoparticle safety concerns. - BPA (Bisphenol A): Plastic containers; endocrine disruptor. - Triclosan: Soap, toiletries; linked to long-term exposure toxicity. |
Cleansing Agents
Soaps vs Detergents
| Compare soaps and detergents: composition, hard water behavior, and biodegradability. | Cleansing Chemistry: - Soaps: Sodium/Potassium salts of fatty acids; form scum in hard water; easily biodegradable; less environmental harm. - Detergents: Ammonium/Sulphonate salts; work effectively in hard water; often non-biodegradable; can cause water pollution. |
Plastics
Plastic Types
| Classify plastics by recycling codes: PET, HDPE, PVC, LDPE, PP, and PS. | - Recycling Codes:
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Environmental Chemicals
Pollutants of Concern
| Identify PFAS, Glyphosate, Oxybenzone, Formaldehyde, and Microplastics. | Environmental Toxicology: - PFAS ("Forever Chemicals"): Non-stick cookware, firefighting foam; persistent in environment and body. - Glyphosate: Widely used herbicide; potential carcinogen. - Oxybenzone: Common chemical sunscreen filter; associated with coral reef bleaching. - Formaldehyde: Industrial glue, furniture; human carcinogen. - Microplastics: Degraded plastic fragments; widespread marine and food chain pollution. |
High-Yield S&T Rapid Revision: Top UPSC Traps
- PSLV: Utilizes four stages (solid-liquid-solid-liquid), whereas GSLV uses three stages (solid-liquid-cryogenic) (ISRO).
- Covishield: Developed on a viral vector platform (adenovirus), not mRNA (ICMR).
- Quantum Computing: Classical bits are strictly 0 or 1, while qubits exploit superposition to exist in multiple states simultaneously (DST).
- Web 3.0: Decentralized web architecture enabling user data ownership via blockchain and DAOs (MeitY).
- NFC: Near Field Communication operating range is limited to approximately 10 centimeters, not 1 meter (DoT).
- Licensed vs. Indigenous: Systems built in India under license/ToT—specifically Su-30 MKI (HAL Nasik, Russian origin), T-90S Bhishma (HVF Avadi, Russian origin), and K9 Vajra-T (L&T Hazira, South Korean origin)—are not indigenous designs (common matching trap).
- Submarine Propulsion Classes: SSBN (nuclear ballistic, e.g., Arihant) vs. SSN (nuclear attack, e.g., leased Chakra) vs. SSK (diesel-electric conventional, e.g., Kalvari). INS Chakra was strictly leased from Russia, not owned or built domestically.
- AWACS & Radar Platforms: DRDO Netra is a co-developed/hybrid system (Indian radar on Brazilian Embraer jet frame), whereas Phalcon is imported (Israeli radar on Russian airframe).
- BrahMos: A joint venture between India (DRDO) and Russia, but is not part of the IGMDP (Prithvi, Agni, Trishul, Akash, Nag).