Physics Wiki
Theory Catalog
Browse physics concepts in reference-style articles focused on definitions, equations, and intuition.
Theory Catalog
Build intuition with concise theory notes you can revisit while learning and problem-solving.
Beginner
#momentum
Momentum
A vector quantity that measures motion and is conserved in isolated systems.
Intermediate
#conservation
Conservation of Momentum
Total momentum stays constant in a closed system, even during collisions.
Beginner
#energy
Kinetic Energy
Moving bodies carry energy proportional to mass and speed squared.
Beginner
#conservation
Conservation of Energy
In ideal systems, energy changes form but total mechanical energy stays constant.
Intermediate
#collision
Elastic Collision
Elastic collisions preserve both momentum and kinetic energy.
Beginner
#pendulum
Small-Angle Approximation
When angle is small, sin(theta) can be approximated by theta.
Beginner
#oscillation
Simple Harmonic Motion
Linear restoring forces produce sinusoidal oscillation.
Beginner
#spring
Hooke's Law
Spring restoring force is proportional to displacement in linear range.
Intermediate
#damping
Damped Oscillation
Resistive effects remove energy and reduce amplitude over time.
Advanced
#nonlinear
Nonlinear Dynamics
Coupled pendulum systems follow nonlinear equations with rich behavior.
Advanced
#chaos
Chaos and Sensitivity
Deterministic systems can still be highly sensitive to initial conditions.
Advanced
#lagrangian
Lagrangian Mechanics
Complex coupled systems are often derived from energy-based variational principles.
Advanced
#numerical
Numerical Integration
Nonlinear systems are typically solved by time-stepping methods.