General Knowledge
Beginner Level
Physics
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Jun 30, 2026
About This Cheat Sheet
Hey there! Welcome to your complete guide to Physics for competitive exams. I've put together everything you need to know in one place — from Mechanics, Gravitation, and Thermodynamics to Optics, Waves, Sound, Electricity, Magnetism, and more. Whether you're preparing for SSC, Banking, Railways, UPSC, or State PSC exams, this cheat sheet covers important laws, SI units, formulas, scientists, and shortcut techniques to help you score better.
⚙️ Mechanics
- Motion - Displacement, Speed, Velocity
- Acceleration - Rate of change of velocity
- Newton's Laws - 3 Laws of Motion
- Friction - Opposes motion
- Work - Force × Distance
- Energy - Kinetic, Potential
- Power - Work ÷ Time
- Momentum - Mass × Velocity
🌍 Gravitation
- Universal Law - F = G(m₁m₂)/r²
- Acceleration due to Gravity - g = 9.8 m/s²
- Escape Velocity - 11.2 km/s (Earth)
- Orbital Velocity - 7.9 km/s (Earth)
- Satellites - Geostationary, Polar
- Weight - Mass × Gravity
- Gravity - Attractive force
- Kepler's Laws - Planetary motion
🔥 Thermodynamics
- Heat - Transfer of energy
- Temperature - Measure of heat
- Thermal Expansion - Expansion on heating
- Specific Heat - Heat per unit mass
- Laws of Thermodynamics - 4 Laws
- Entropy - Measure of disorder
- Heat Engines - Convert heat to work
- Refrigerators - Transfer heat
💡 Optics
- Reflection - Bouncing of light
- Mirrors - Concave, Convex, Plane
- Refraction - Bending of light
- Lenses - Concave, Convex
- Dispersion - Splitting of white light
- Rainbow - Dispersion of light
- Scattering - Blue sky, Red sunset
- Optical Instruments - Microscope, Telescope
🔊 Waves & Sound
- Wave Motion - Transverse, Longitudinal
- Wavelength - Distance between crests
- Frequency - Cycles per second (Hz)
- Speed of Sound - 340 m/s (air)
- Reflection of Sound - Echo, Reverberation
- Ultrasound - > 20,000 Hz
- Infrasound - < 20 Hz
- Doppler Effect - Change in frequency
⚡ Electricity & Magnetism
- Electric Charge - Coulomb (C)
- Current - Ampere (A)
- Voltage - Volt (V)
- Resistance - Ohm (Ω)
- Ohm's Law - V = IR
- Power - P = VI
- Magnetic Effect - Electromagnetism
- Electromagnetic Induction - Faraday's Law
⚙️ Newton
3 Laws of Motion
F = ma🌍 Gravity
g = 9.8 m/s²
Escape Velocity: 11.2 km/s⚡ Ohm's Law
V = IR
Current, Voltage, Resistance🔊 Sound
Speed = 340 m/s
Air medium⚙️ Newton's Laws of Motion
📚 First Law (Inertia)
- Statement: Objects remain at rest or in uniform motion unless acted upon by a force
- Example: A book remains on a table unless pushed
- Key Point: Inertia = Resistance to change
📚 Second Law (F = ma)
- Statement: Force equals mass times acceleration
- Formula: F = m × a
- Key Point: Heavier objects require more force
📚 Third Law (Action-Reaction)
- Statement: For every action, there is an equal and opposite reaction
- Example: Rocket propulsion
- Key Point: Forces always act in pairs
📐 Important Physics Formulas
Speed: v = d/t (Distance ÷ Time)
Acceleration: a = (v - u)/t (Change in velocity ÷ Time)
Force: F = m × a (Mass × Acceleration)
Work: W = F × d (Force × Distance)
Kinetic Energy: KE = ½mv² (Half × Mass × Velocity²)
Potential Energy: PE = mgh (Mass × Gravity × Height)
Power: P = W/t (Work ÷ Time)
Momentum: p = m × v (Mass × Velocity)
📐 More Physics Formulas
Gravitation: F = G(m₁m₂)/r²
Gravity: g = GM/r²
Escape Velocity: vₑ = √(2GM/r)
Ohm's Law: V = IR (Voltage = Current × Resistance)
Power (Electric): P = VI (Voltage × Current)
Wave Speed: v = fλ (Frequency × Wavelength)
Lens Formula: 1/f = 1/v - 1/u
Magnification: m = -v/u
📊 Important SI Units
📏 Fundamental Units
- Length: Metre (m)
- Mass: Kilogram (kg)
- Time: Second (s)
- Electric Current: Ampere (A)
- Temperature: Kelvin (K)
- Amount: Mole (mol)
- Luminous Intensity: Candela (cd)
⚙️ Derived Units
- Force: Newton (N) = kg·m/s²
- Energy: Joule (J) = N·m
- Power: Watt (W) = J/s
- Pressure: Pascal (Pa) = N/m²
- Frequency: Hertz (Hz) = 1/s
- Charge: Coulomb (C) = A·s
- Resistance: Ohm (Ω) = V/A
⚡ Electrical Units
- Voltage: Volt (V)
- Current: Ampere (A)
- Resistance: Ohm (Ω)
- Capacitance: Farad (F)
- Inductance: Henry (H)
- Conductance: Siemens (S)
- Magnetic Flux: Weber (Wb)
🔬 Scientific Units
- Pressure: Pascal (Pa)
- Energy: Joule (J)
- Power: Watt (W)
- Temperature: Kelvin (K)
- Frequency: Hertz (Hz)
- Magnetic Field: Tesla (T)
- Luminous Flux: Lumen (lm)
💡 Optics: Reflection & Refraction
🪞 Reflection of Light
- Law 1: Angle of incidence = Angle of reflection
- Law 2: Incident ray, reflected ray, and normal lie in the same plane
- Types: Regular (smooth surface), Diffused (rough surface)
- Mirrors: Concave, Convex, Plane
🔦 Refraction of Light
- Definition: Bending of light when changing medium
- Snell's Law: n₁sinθ₁ = n₂sinθ₂
- Index of Refraction: n = c/v
- Examples: Glass slab, Prism, Lenses
🔍 Lenses
- Concave Lens: Diverging (Negative focal length)
- Convex Lens: Converging (Positive focal length)
- Lens Formula: 1/f = 1/v - 1/u
- Magnification: m = -v/u
💡 Optical Phenomena
🌈 Dispersion
- Definition: Splitting of white light into colors
- Colors: VIBGYOR (Violet, Indigo, Blue, Green, Yellow, Orange, Red)
- Example: Rainbow
- Cause: Different wavelengths bend differently
☀️ Scattering of Light
- Blue Sky: Shorter wavelengths (blue) scatter more
- Red Sunset: Longer wavelengths (red) scatter less
- Tyndall Effect: Scattering of light by particles
- Example: Sunlight through dust
👁️ Human Eye
- Myopia: Near-sightedness (Concave lens)
- Hypermetropia: Far-sightedness (Convex lens)
- Presbyopia: Age-related vision loss (Bifocal lens)
- Astigmatism: Irregular curvature (Cylindrical lens)
🔬 Optical Instruments
🔬 Microscope
- Use: Viewing small objects
- Types: Simple, Compound
- Lens: Convex lenses
- Magnification: High
🔭 Telescope
- Use: Viewing distant objects
- Types: Refracting, Reflecting
- Lens: Convex objective lens
- Magnification: Very high
📷 Camera
- Use: Capturing images
- Lens: Convex lens
- Sensor: Film or digital
- Focus: Adjustable
🔄 Periscope
- Use: Viewing from hidden position
- Mirrors: Plane mirrors
- Angle: 45° reflection
- Use in: Submarines, tanks
⚡ Electricity & Magnetism
⚡ Electric Charge
- Unit: Coulomb (C)
- Types: Positive, Negative
- Law: Like charges repel, unlike attract
- Current: Rate of flow of charge (I = Q/t)
🔌 Ohm's Law
- Statement: V = IR
- V: Voltage (Volts)
- I: Current (Amperes)
- R: Resistance (Ohms)
⚡ Electric Power
- Formula: P = VI = I²R = V²/R
- Unit: Watt (W)
- Heating Effect: H = I²Rt (Joule's Law)
- Appliances: Heater, Iron, Bulb
🧲 Magnetism & Electromagnetism
🧲 Magnetic Effect
- Current carrying wire: Produces magnetic field
- Right-Hand Rule: Direction of magnetic field
- Solenoid: Coil of wire (Electromagnet)
- Motor: Electric Motor (Electrical → Mechanical)
⚡ Electromagnetic Induction
- Faraday's Law: Induced EMF = -dΦ/dt
- Lenz's Law: Induced current opposes change
- Generator: Mechanical → Electrical
- Transformer: Changes voltage (Step-up, Step-down)
🔄 AC vs DC
- AC: Alternating Current (changes direction)
- DC: Direct Current (constant direction)
- AC: Used in homes (220V, 50Hz)
- DC: Used in batteries, electronics
🔊 Waves & Sound
🌊 Wave Motion
- Transverse: Perpendicular to direction (Light)
- Longitudinal: Parallel to direction (Sound)
- Wavelength: Distance between crests
- Frequency: Cycles per second (Hz)
- Amplitude: Height of wave
🔊 Sound
- Speed in Air: 340 m/s
- Speed in Water: 1480 m/s
- Speed in Steel: 5100 m/s
- Ultrasound: > 20,000 Hz (Medical imaging)
- Infrasound: < 20 Hz (Earthquakes)
🔄 Doppler Effect
- Definition: Change in frequency due to relative motion
- Example: Siren of approaching vehicle
- Application: Radar, Medical ultrasound
- Astronomy: Redshift/Blueshift
🔬 Important Physics Scientists
🍎 Isaac Newton
- Contribution: Laws of Motion, Universal Gravitation
- Key: F = ma, Law of Gravity
- Book: Principia Mathematica
🧠 Albert Einstein
- Contribution: Theory of Relativity
- Key: E = mc²
- Nobel: 1921 (Photoelectric effect)
🔬 Marie Curie
- Contribution: Radioactivity, Radium
- Key: Discovered Polonium, Radium
- Nobel: Physics (1903), Chemistry (1911)
⚡ Nikola Tesla
- Contribution: AC current, Alternating Current
- Key: Induction motor, Tesla coil
- Legacy: AC power distribution
🔬 More Physics Scientists
⚡ Michael Faraday
- Contribution: Electromagnetic Induction
- Key: Faraday's Law, Faraday Cage
- Unit: Farad (Capacitance)
⚡ James Clerk Maxwell
- Contribution: Electromagnetic Theory
- Key: Maxwell's Equations
- Predicted: Electromagnetic waves
🔬 C.V. Raman
- Contribution: Raman Effect
- Key: Scattering of light
- Nobel: 1930 (First Asian)
🔭 Galileo Galilei
- Contribution: Telescope, Motion studies
- Key: Free fall, Heliocentrism
- Title: Father of Science
🎯 Physics Quick Revision
The Golden Rule: Focus on formulas, SI units, and important laws. Most competitive exam questions test your ability to recall formulas, match quantities with units, and apply laws to real-world scenarios.
Quick Memory Tricks:
- 📌 Newton's Laws: "Inertia (1st), F=ma (2nd), Action-Reaction (3rd)"
- 📌 Optics: "Reflection = Bouncing, Refraction = Bending, Dispersion = Splitting"
- 📌 Electricity: "V = IR (Ohm's Law), P = VI (Power)"
- 📌 Sound Speed: "Air = 340, Water = 1480, Steel = 5100"
- 📌 Gravity: "g = 9.8, Escape = 11.2, Orbital = 7.9"
Exam Strategy:
- Step 1: Read the question — identify the topic (Mechanics, Optics, Electricity, etc.)
- Step 2: Recall the relevant formula or law
- Step 3: Match units and symbols correctly
- Step 4: For scientific instruments, remember their use
- Step 5: For scientists, match with their contribution
💡 Pro Tips for Physics
✅ Memorize Key Formulas
F = ma, V = IR, P = VI, v = fλ, W = F × d. These appear in almost every exam.
✅ Learn SI Units
Newton (Force), Joule (Energy), Watt (Power), Pascal (Pressure), Hertz (Frequency).
✅ Understand Laws
Newton's Laws, Ohm's Law, Faraday's Law, Snell's Law — know their statements and applications.
✅ Optics Concepts
Reflection (Mirrors), Refraction (Lenses), Dispersion (Rainbow), Scattering (Blue sky).
✅ Sound & Waves
Speed of sound in different media, Doppler Effect, Ultrasound uses, Echo vs Reverberation.
✅ Famous Scientists
Newton (Gravity/Motion), Einstein (Relativity), Faraday (Induction), Raman (Raman Effect).
📊 Quick Reference: SI Units Summary
📏 Quantity
- Length
- Mass
- Time
- Current
- Temperature
- Amount
- Force
- Energy
- Power
- Pressure
- Frequency
- Charge
- Resistance
📚 SI Unit
- Metre (m)
- Kilogram (kg)
- Second (s)
- Ampere (A)
- Kelvin (K)
- Mole (mol)
- Newton (N)
- Joule (J)
- Watt (W)
- Pascal (Pa)
- Hertz (Hz)
- Coulomb (C)
- Ohm (Ω)
🎯 Symbol
- m
- kg
- s
- A
- K
- mol
- N
- J
- W
- Pa
- Hz
- C
- Ω
📝 Formula
- -
- -
- -
- -
- -
- -
- kg·m/s²
- N·m
- J/s
- N/m²
- 1/s
- A·s
- V/A
🔬 Quick Reference: Optical Instruments Summary
🔬 Instrument
- Microscope
- Telescope
- Camera
- Periscope
- Binoculars
- Endoscope
- Spectrometer
🎯 Use
- View small objects
- View distant objects
- Capture images
- View from hidden position
- View distant objects (2 eyes)
- Internal body viewing
- Measure wavelengths
🔧 Principle
- Refraction (Lenses)
- Refraction/Reflection
- Refraction (Lens)
- Reflection (Mirrors)
- Refraction (Lenses)
- Total Internal Reflection
- Dispersion/Refraction
⚙️ Key Component
- Convex lenses
- Objective lens
- Convex lens
- Plane mirrors
- Convex lenses
- Optical fiber
- Prism/Grating
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