1. Force, Motion & Mechanics
| Application | Principle |
| Washing machine | Centrifugal effect |
| Cream separator | Centrifugal effect |
| Banking of roads | Centripetal force |
| Seat belt | Inertia |
| Rocket | Conservation of momentum / Newton’s third law |
| Gun recoil | Conservation of momentum |
| Walking | Newton’s third law |
| Swimming | Newton’s third law |
| Rowing a boat | Newton’s third law |
| Jumping from a boat | Conservation of momentum |
| Car turning on a road | Centripetal force |
| Stone tied to a string and whirled | Centripetal force |
2. Work, Energy & Machines
| Application | Principle |
| Hydroelectric power plant | Potential → kinetic → electrical energy |
| Dam | Gravitational potential energy |
| Pendulum | PE ↔ KE |
| Bow and arrow | Elastic potential energy |
| Spring toy | Elastic potential energy |
| Hammer driving a nail | Mechanical work |
| Bicycle | Chemical → mechanical energy |
| Electric motor | Electrical → mechanical energy |
| Generator | Mechanical → electrical energy |
| Solar cell | Solar → electrical energy |
3. Heat & Thermal Physics
| Application | Principle |
| Sea breeze | Differential heating + convection |
| Land breeze | Differential heating + convection |
| Chimney | Convection |
| Ventilators near ceiling | Hot air rises |
| Woollen clothes | Poor conduction / trapped air |
| Thermos flask | Minimizes conduction, convection and radiation |
| Black clothes | Good absorbers of radiation |
| White clothes | Reflect more radiation |
| Pressure cooker | Increased pressure → higher boiling point |
| Refrigerator | Refrigeration cycle / heat transfer |
| Desert cooler | Evaporation |
| Sweating | Evaporation |
| Earthen pot | Evaporation |
| Ice wrapped in sawdust | Poor conduction |
| Metal spoon feels colder | Metal conducts heat faster |
| Railway track gaps | Thermal expansion |
| Electric wire slack | Thermal expansion/contraction |
4. Pressure & Fluids
| Application | Principle |
| Sharp knife | Small area → high pressure |
| Sharp needle | Small area → high pressure |
| Broad school-bag straps | Large area → low pressure |
| Camel’s feet | Reduced pressure on sand |
| Broad tractor tyres | Reduced pressure on soil |
| High heels | Small area → high pressure |
| Hydraulic press | Pascal’s law |
| Hydraulic lift | Pascal’s law |
| Hydraulic brakes | Pascal’s law |
| Syringe | Pressure difference |
| Straw | Atmospheric pressure |
| Suction cup | Atmospheric pressure |
| Dam walls thicker at bottom | Pressure increases with depth |
| Ship | Archimedes’ principle / buoyancy |
| Submarine | Buoyancy / density |
| Hydrometer | Buoyancy / relative density |
5. Sound
| Application | Principle |
| Echo | Reflection of sound |
| SONAR | Ultrasonic waves + reflection |
| Medical ultrasound | Ultrasonic waves |
| Bats | Ultrasound + echolocation |
| Dog whistle | High-frequency/ultrasonic sound |
| Noise reduction | Sound absorption |
| Auditorium design | Controlled reflection + absorption |
| Megaphone | Multiple reflection |
| Stethoscope | Transmission/reflection of sound |
| Doppler effect | Apparent change in frequency due to relative motion |
6. Light & Optics
| Application | Principle |
| Rear-view mirror | Convex mirror |
| Side-view mirror | Convex mirror |
| Dentist’s mirror | Concave mirror |
| Shaving mirror | Concave mirror |
| Solar furnace | Concave mirror |
| Vehicle headlights | Concave reflector |
| Periscope | Reflection |
| Kaleidoscope | Multiple reflection |
| Rainbow | Dispersion + refraction + internal reflection |
| Mirage | Refraction + total internal reflection |
| Optical fibre | Total internal reflection |
| Diamond shines brightly | Total internal reflection |
| Magnifying glass | Convex lens |
| Camera | Convex lens |
| Projector | Convex lens |
| Microscope | Convex lenses |
| Telescope | Lenses/mirrors |
| Human eye | Convex lens |
| Myopia | Concave lens |
| Hypermetropia | Convex lens |
| Astigmatism | Cylindrical lens |
7. Electricity & Magnetism
| Application | Principle |
| Fuse | Heating effect of current |
| Electric heater | Heating effect |
| Electric iron | Heating effect |
| Toaster | Heating effect |
| Incandescent bulb | Heating effect |
| Electric bell | Electromagnetism |
| Electric motor | Magnetic effect of current |
| Generator | Electromagnetic induction |
| Transformer | Electromagnetic induction |
| Loudspeaker | Electromagnetism |
| Microphone | Sound → electrical signal |
| Doorbell | Electromagnet |
| MCB | Protection from excessive current |
| Lightning conductor | Safe path for electrical discharge |
| Earthing | Protection against electric shock |
8. Nuclear Physics & Modern Physics
| Application | Principle |
| Sun | Nuclear fusion |
| Nuclear reactor | Controlled nuclear fission |
| Atomic bomb | Uncontrolled nuclear fission |
| Hydrogen bomb | Nuclear fusion |
| Solar cell | Photovoltaic effect |
| X-ray machine | Production of X-rays |
| Radiotherapy | Ionizing radiation |
| Nuclear medicine | Radioisotopes |
| Smoke detector | Radioactive radiation |
| Remote control | Infrared radiation |
| TV/radio communication | Electromagnetic waves |
Top 40 Must-Memorize Associations
These are particularly useful for one-line General Science MCQs:
- Washing machine → Centrifugal effect
- Cream separator → Centrifugal effect
- Banking of roads → Centripetal force
- Seat belt → Inertia
- Rocket → Conservation of momentum
- Gun recoil → Conservation of momentum
- Walking → Newton’s third law
- Swimming → Newton’s third law
- Pressure cooker → Higher boiling point
- Desert cooler → Evaporation
- Thermos flask → Reduces heat transfer
- Hydraulic press → Pascal’s law
- Ship → Archimedes’ principle
- Hydrometer → Buoyancy
- Sharp knife → High pressure
- Camel’s feet → Low pressure
- SONAR → Ultrasonic waves + reflection
- Echo → Reflection of sound
- Bats → Echolocation
- Doppler effect → Apparent frequency change
- Rear-view mirror → Convex mirror
- Dentist’s mirror → Concave mirror
- Solar furnace → Concave mirror
- Camera → Convex lens
- Magnifying glass → Convex lens
- Myopia → Concave lens
- Hypermetropia → Convex lens
- Optical fibre → Total internal reflection
- Rainbow → Dispersion
- Kaleidoscope → Multiple reflection
- Electric heater → Heating effect
- Fuse → Heating effect
- Electric bell → Electromagnet
- Motor → Electrical → Mechanical
- Generator → Mechanical → Electrical
- Transformer → Electromagnetic induction
- Sun → Nuclear fusion
- Nuclear reactor → Controlled nuclear fission
- Solar cell → Photovoltaic effect
- Lightning conductor → Safe discharge to Earth