Physics
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Physics – Quick Revision
Physics is a crucial section in General Science for almost all competitive examinations including SSC, Banking, Railway, UPSC, Defence, Insurance, CAT, State PSC, and other government exams.
This quick revision guide covers important facts about Mechanics, Gravitation, Thermodynamics, Optics, Waves & Sound, Electricity, Magnetism, and Nuclear Physics. It is designed for last-minute revision and quick recall of physics facts.
About This Quick Revision
Complete guide to Physics for competitive exams:
Mechanics
- Motion, Speed, Velocity
- Acceleration, Newton's Laws
- Work, Energy, Power
- Momentum, Friction
Gravitation
- Universal Law of Gravitation
- Gravity & Acceleration
- Escape Velocity
- Satellites & Orbits
Thermodynamics
- Heat & Temperature
- Laws of Thermodynamics
- Entropy
- Heat Transfer
Optics
- Reflection & Refraction
- Lenses & Mirrors
- Dispersion & Prism
- Optical Instruments
Waves & Sound
- Wave Motion
- Echo & Doppler Effect
- Ultrasound
- Frequency & Wavelength
Electricity & Magnetism
- Electric Charge & Current
- Voltage & Resistance
- Ohm's Law
- Electromagnetic Induction
Nuclear Physics
- Radioactivity
- Alpha, Beta, Gamma
- Nuclear Fission & Fusion
- Nuclear Reactors
Important Scientists
- Newton, Einstein
- Galileo, Tesla
- Faraday, Maxwell
- Raman, Curie
Key Topics Covered
This quick revision guide covers important Physics topics for competitive exams:
| Category | Topic | Key Facts |
|---|---|---|
| Mechanics | Motion, Newton's Laws, Work, Energy, Power | F=ma, KE=½mv², PE=mgh, Power=F×v |
| Gravitation | Universal Law, Gravity, Escape Velocity | F=Gm₁m₂/r², g=9.8 m/s², Ve=√(2GM/R) |
| Thermodynamics | Heat, Temperature, Laws, Entropy | Heat transfer, 1st Law: ΔU=Q-W, 2nd Law: Entropy increases |
| Optics | Reflection, Refraction, Lenses, Dispersion | Mirror: 1/f=1/v+1/u, Snell's Law: n₁sinθ₁=n₂sinθ₂ |
| Waves & Sound | Wave Motion, Doppler Effect, Ultrasound | v=fλ, Doppler effect, Sonic boom |
| Electricity | Charge, Current, Voltage, Resistance, Ohm's Law | V=IR, P=VI, Series/Parallel combination |
| Magnetism | Electromagnetic Induction, Motors, Generators | Faraday's Law, Lenz's Law, AC/DC |
| Nuclear Physics | Radioactivity, Fission, Fusion | Alpha (α), Beta (β), Gamma (γ), E=mc² |
Physics at a Glance
⚡ Key Constants
Speed of Light: 3×10⁸ m/s | Gravitational Constant (G): 6.67×10⁻¹¹ N·m²/kg² | Acceleration due to gravity (g): 9.8 m/s²
📐 Important Formulas
F = ma | KE = ½mv² | PE = mgh | P = IV | V = IR | E = mc² | v = fλ
🔬 SI Units
Force: Newton (N) | Energy: Joule (J) | Power: Watt (W) | Pressure: Pascal (Pa) | Frequency: Hertz (Hz)
🌍 Important Scientists
Newton (Laws of Motion) | Einstein (Relativity) | Faraday (Electromagnetic Induction) | Tesla (AC Current)
Quick Comparison: Newton's Laws of Motion
Why This Quick Revision is Important
Complete Physics Coverage
Covers Mechanics, Gravitation, Optics, Electricity, Magnetism, and Nuclear Physics.
Quick Reference Tables
Important formulas, constants, and SI units presented in easy-to-remember formats.
Visual Learning Aids
Tables and cards make complex physics concepts easy to understand.
High Exam Weightage
Physics questions appear frequently in all competitive examinations.
Competitive Exams Covered
- SSC CGL
- SSC CHSL
- SSC MTS
- Bank PO & Clerk
- IBPS Exams
- Railway Recruitment Exams
- UPSC CSAT
- Defence Exams
- Insurance Exams
- CAT
- State Government Exams
Quick Revision Examples
Question 1:
What is Newton's Second Law of Motion and give its formula?
Answer: F = ma (Force = Mass × Acceleration)
Key Fact: Newton's Second Law states that the force acting on an object is equal to its mass multiplied by its acceleration. The SI unit of force is Newton (N).
Question 2:
What is Newton's Universal Law of Gravitation?
Answer: Every particle attracts every other particle with a force directly proportional to the product of their masses and inversely proportional to the square of the distance between them
Key Fact: The formula is F = G × m₁ × m₂ / r², where G is the gravitational constant (6.67 × 10⁻¹¹ N·m²/kg²).
Question 3:
What is the speed of light in a vacuum?
Answer: 3 × 10⁸ meters per second
Key Fact: The speed of light is approximately 3 × 10⁸ m/s (about 300,000 km/s). It is the fastest speed in the universe and is denoted by the letter 'c' in physics equations like E = mc².
Question 4:
What is Ohm's Law and give its formula?
Answer: V = IR (Voltage = Current × Resistance)
Key Fact: Ohm's Law states that the current flowing through a conductor is directly proportional to the voltage applied across it, provided the temperature remains constant. The unit of resistance is Ohm (Ω).
Question 5:
What is Snell's Law of Refraction?
Answer: n₁ × sin θ₁ = n₂ × sin θ₂
Key Fact: Snell's Law describes the relationship between the angles of incidence and refraction when light passes through different media. It is used in lenses, prisms, and optical fibers.
Question 6:
What is Einstein's most famous equation and what does it represent?
Answer: E = mc² – Represents the equivalence of mass and energy
Key Fact: E = mc² states that energy equals mass times the speed of light squared. This equation is the basis of nuclear energy and atomic bombs. It was proposed by Albert Einstein in 1905.
Question 7:
What is escape velocity and what is its value on Earth?
Answer: Escape velocity is the minimum velocity required to escape Earth's gravitational field. Value: 11.2 km/s
Key Fact: Escape velocity formula: Ve = √(2GM/R). On Earth, it is 11.2 km/s. For the Moon, it is 2.38 km/s.
Question 8:
What is the formula for power and what is its SI unit?
Answer: Power = Work / Time = Force × Velocity; SI Unit: Watt (W)
Key Fact: Power is the rate of doing work. 1 Watt = 1 Joule per second. The formula is P = W / t = F × v. Horsepower (hp) is also a unit of power (1 hp = 746 W).
Question 9:
Who discovered electromagnetic induction and what does it state?
Answer: Michael Faraday – Electromagnetic induction states that a changing magnetic field induces an electric current in a conductor
Key Fact: Faraday discovered electromagnetic induction in 1831. This principle is used in generators, transformers, and electric motors.
Question 10:
What are alpha (α), beta (β), and gamma (γ) radiation?
Answer: Alpha: Helium nucleus (⁴He²⁺), Beta: Electron (e⁻) or Positron (e⁺), Gamma: High-energy electromagnetic radiation
Key Fact: Alpha has the least penetration, gamma has the most. Alpha is stopped by paper, beta by aluminum, and gamma by lead. Radioactivity was discovered by Henri Becquerel.
Question 11:
What is the wave equation and what do the symbols represent?
Answer: v = fλ (Velocity = Frequency × Wavelength)
Key Fact: This equation relates wave speed, frequency, and wavelength. The unit of frequency is Hertz (Hz), and wavelength is measured in meters. The speed of sound in air is 344 m/s.
Final Takeaway
Physics is a vital section in all competitive exams. Regular revision of key facts about Mechanics, Gravitation, Optics, Electricity, Magnetism, and Nuclear Physics can significantly improve your score.
This quick revision guide serves as a comprehensive resource for last-minute preparation. Focus on remembering important formulas, constants, laws, and SI units presented in tables and cards for quick recall during exams.
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