Quick answer
Physics is usually divided into six core branches: classical mechanics, kinematics, thermodynamics, waves and optics, electromagnetism and modern physics. Each branch studies a different part of nature, but they all share the same ideas of force, energy and fields. Pick one of the branches of physics below to start learning.
The Six Core Branches of Physics
Classical Mechanics
How forces change the motion of objects, from rolling balls to orbiting planets.
- Newton’s laws of motion
- Work, energy and power
- Momentum and collisions
Kinematics
Describing motion with displacement, velocity, acceleration and time.
- SUVAT equations
- Motion graphs
- Projectile motion
Thermodynamics
How heat and work move energy between systems.
- Specific heat capacity
- Gas laws and PV = nRT
- Heat engines
Waves & Optics
How energy travels as waves, including sound and light.
- The wave equation v = fλ
- Refraction and Snell’s law
- Interference and diffraction
Electromagnetism
Electric charge, circuits, magnetic fields and induction.
- Ohm’s law
- Series and parallel circuits
- Electromagnetic induction
Modern Physics
Physics at very high speeds and very small scales.
- Special relativity and E = mc²
- The photoelectric effect
- Radioactive decay and half-life
Which Branch Should You Start With?
Most courses begin with kinematics and classical mechanics, because ideas like velocity, force and energy appear in every other branch. Once those feel comfortable, move on to waves, thermodynamics and electromagnetism, and finish with modern physics, which builds on everything before it.