Physics Fundamentals
Explained Simply

🌍 What is Physics?

Physics is the science that studies how things move, how energy works, and how the universe is built. Think of it this way — when you throw a ball up, it comes back down. When you switch on a bulb, it glows. When you feel warm sitting near a fire — all of this is physics!

Physics is one of the oldest sciences in the world. It asks simple but big questions like: Why do things fall? Why is the sky blue? What is matter made of? How did the universe begin?

Mechanics is the branch of physics fundamentals that studies how objects move and why they move. Imagine watching a ball rolling down a hill. Why does it roll? How fast does it go? When does it stop? Mechanics answers all of these questions using simple rules called laws.

• ⭐ Newton's First Law (Inertia): An object keeps doing what it is doing — staying still or moving in a straight line — unless a force pushes or pulls it. Example: A book on a table stays still until you push it.
• ⭐ Newton's Second Law (F = ma): The bigger the force, the bigger the acceleration. The heavier the object, the more force needed to move it.
• ⭐ Newton's Third Law (Action-Reaction): When you push a wall, the wall pushes back on you with the same force. A rocket goes up because gas pushes down!
• ⭐ Energy Conservation: Energy cannot be created or destroyed, only changed from one form to another. A roller coaster converts potential energy to kinetic energy.
• ⭐ Momentum: A moving object is harder to stop if it is heavy or moving fast. A truck is much harder to stop than a bicycle at the same speed.

• 0️⃣ Zeroth Law: If object A and object B are both at the same temperature as object C, then A and B are also at the same temperature. This defines what temperature means.
• 1️⃣ First Law (Energy Conservation): Energy cannot be created or destroyed. You can add heat to a gas and it will either do work or warm up the gas. Total energy stays the same.
• 2️⃣ Second Law (Entropy): Heat flows naturally from hot things to cold things — never the other way! A hot cup of tea always cools down in a room. It never gets hotter on its own.
• 3️⃣ Third Law: As temperature drops toward absolute zero (−273.15°C), the entropy (disorder) of a system approaches zero. You can never actually reach absolute zero.

In the 1800s, scientists discovered something amazing — electricity and magnetism are connected! A moving electric charge creates a magnetic field. A changing magnetic field creates an electric current. Maxwell put this all together into 4 equations that describe how light, electricity, and magnetism all work.

• ⭐ Electric Field: Every electric charge has an invisible force field around it. Positive charges attract negative ones and repel positive ones.
• ⭐ Ohm's Law (V = IR): Voltage is like water pressure. Current is like water flow. Resistance is like the pipe size. More pressure = more flow!
• ⭐ Electromagnetic Induction: Moving a magnet through a coil of wire creates electricity. This is how all power stations in the world generate electricity!
• ⭐ Light as EM Wave: Visible light, X-rays, radio waves, and microwaves are all the same thing — electromagnetic waves — just at different frequencies.

• ⭐ Wave-Particle Duality: Electrons and photons behave like particles sometimes and like waves other times. It depends on how you observe them!
• ⭐ Quantum Superposition: A particle can be in multiple states at the same time — until you look at it. When you measure it, it picks one state. This is like Schrödinger's Cat — the cat is both alive and dead until you open the box!
• ⭐ Heisenberg Uncertainty: You can never know both the exact position and exact speed of a particle at the same time. The more you know one, the less you know the other.
• ⭐ Quantum Entanglement: Two particles can be "entangled" — when you measure one, the other instantly knows, even if they are on opposite sides of the universe!
• ⭐ Quantum Tunnelling: A particle can pass through a wall it should not be able to cross! This happens in the Sun (making it shine) and in computer transistors.