Physics
Energy and work
Work, kinetic and potential energy, power, conservation.
Basics
Work
W = F · s = F s cosθ. If force is perpendicular to displacement, work is zero (centripetal force in uniform circular motion). Unit: J = N·m.
Mechanical energy
With only conservative forces, K+U is constant. Friction and drag are non-conservative: mechanical energy falls and heat rises. Energy changes form, not total amount (closed system).
Formulas
Kinetic energy
Proportional to speed squared. Work–energy: W_net = ΔK.
Gravitational potential energy
The zero of h is a choice; only differences matter.
Symbols
-
hheight
Elastic potential energy
Hooke's law. k is the spring constant; x is displacement from equilibrium.
Symbols
-
kspring constant (N/m) -
xdisplacement
Power
Rate of doing work or transferring energy. Unit W = J/s.
In this field
Mechanics
Kinematics, Newton, momentum, circular motion.
Waves and thermodynamics
Oscillation, waves, sound, heat, entropy.
Electromagnetism and modern physics
Charge, fields, basic circuits, photons, mass–energy.
Fluids and optics
Pressure, buoyancy, Bernoulli, lenses, interference.
Relativity and nuclear sketch
Time dilation, length contraction, decay, cross-section.
Quantum sketch
Photons, matter waves, uncertainty.
Gravity and orbits
Newton's gravity, Kepler, surface g, and circular orbits.
Rotation
Angular velocity, moment of inertia, torque, angular momentum, rolling.
SHM and resonance
Springs and pendulums, energy swap, damping, driving, and resonance.
Electrostatics
Coulomb force, electric field, potential, and a Gauss-law sketch.
Magnetostatics
Lorentz force, Biot–Savart, Ampère, and the solenoid.