Physics
Complete Notes — Easy English
Mechanics · Thermodynamics · Electricity · Waves · Complete Curriculum
Mechanics - Forces and Motion
Newton's Laws and Kinematics
Newton's First Law
Object in motion stays in motion; object at rest stays at rest unless acted upon by force.
Newton's Second Law
F = ma (Force equals mass times acceleration)
Newton's Third Law
For every action, there is equal and opposite reaction.
Kinematic Equations
- v = u + at
- s = ut + ½at²
- v² = u² + 2as
Types of Motion
| Type | Definition |
|---|---|
| Uniform | Constant velocity |
| Non-uniform | Changing velocity |
| Circular | Constant speed, changing direction |
Work, Energy and Power
Fundamental Concepts
Work Definition
W = F·d·cosθ (Force × displacement × angle)
Forms of Energy
- Kinetic: KE = ½mv²
- Potential: PE = mgh
- Elastic: Stored in springs
- Thermal: Heat energy
Conservation of Energy
Total mechanical energy remains constant if no external forces act.
Power
P = W/t (Power = Work / Time)
Unit: Watt (W) = Joule/second
Thermodynamics
Heat and Temperature
Temperature vs Heat
- Temperature: Measure of particle motion
- Heat: Transfer of thermal energy
Laws of Thermodynamics
| Law | Statement |
|---|---|
| Zeroth | Thermal equilibrium concept |
| First | Energy conservation (Q = ΔU + W) |
| Second | Entropy always increases |
| Third | Absolute zero unattainable |
Heat Transfer Methods
- Conduction: Direct contact
- Convection: Fluid movement
- Radiation: Electromagnetic waves
Electricity - Charge and Current
Fundamental Concepts
Electric Charge
- Positive: Protons
- Negative: Electrons
- Unit: Coulomb (C)
Coulomb's Law
F = k(q₁q₂)/r² (Force between charges)
Electric Current
I = Q/t (Charge per unit time)
Unit: Ampere (A)
Resistance
R = ρL/A (Resistivity × length / area)
Ohm's Law: V = IR
| Component | Symbol | Unit |
|---|---|---|
| Voltage | V | Volt |
| Current | I | Ampere |
| Resistance | R | Ohm |
Magnetism
Magnetic Fields and Properties
Magnetic Poles
- North Pole: Attracts south
- South Pole: Attracts north
- Opposite poles attract; same poles repel
Magnetic Field
Region where magnetic force acts on moving charges or magnetic materials.
Earth's Magnetic Field
- Protects from solar radiation
- Geographic north ≠ Magnetic north
- Declination varies by location
Applications
- Compasses for navigation
- Motors and generators
- Medical imaging (MRI)
Electromagnetism
Connection Between Electricity and Magnetism
Electromagnetic Induction
Moving magnetic field induces electric current.
Faraday's Law
ε = -dΦ/dt (Induced EMF proportional to flux change)
Lenz's Law
Induced current opposes the change causing it.
Electromagnetic Spectrum
- Radio waves (longest)
- Microwaves, Infrared
- Visible light
- Ultraviolet, X-rays
- Gamma rays (shortest)
Waves and Sound
Wave Properties and Behavior
Wave Properties
- Wavelength (λ): Distance between crests
- Frequency (f): Waves per second
- Amplitude: Maximum displacement
- Period (T): Time for one cycle
Wave Equation
v = fλ (Velocity = frequency × wavelength)
Sound Waves
| Property | Value |
|---|---|
| Speed in air (20°C) | 343 m/s |
| Speed in water | 1480 m/s |
| Frequency range (human) | 20 Hz - 20,000 Hz |
Wave Phenomena
- Reflection: Bounces off surface
- Refraction: Bends at boundary
- Interference: Waves combine
- Diffraction: Spreads around obstacle
Light and Optics
Properties of Light
Nature of Light
- Wave: Exhibits interference, diffraction
- Particle: Exhibits photoelectric effect
- Speed: 3×10⁸ m/s (vacuum)
Laws of Reflection
- Angle of incidence = Angle of reflection
- Incident ray, reflected ray, normal are coplanar
Refraction
Snell's Law: n₁sinθ₁ = n₂sinθ₂
n = refractive index
Optical Devices
| Device | Purpose |
|---|---|
| Lens | Converge/diverge light |
| Mirror | Reflect light |
| Prism | Disperse light |
✨ Congratulations!
You've completed Physics! Understand the laws of nature and universe.
