One map of physics, three ways in. Drill down on any quantity to see its units, the equations it lives in, and how its values span the universe.
Browse physics field by field. Each equation is interactive — click any symbol chip to drill into the underlying quantity, its units, and the equations it appears in.
Motion, forces, energy and the dynamics of bodies.
The net force on a body equals its mass times its acceleration.
Momentum is the product of mass and velocity.
Impulse equals change in momentum.
The energy a body possesses due to its motion.
Work equals force times displacement along the force.
Every mass attracts every other with a force following an inverse-square law.
Magnitude of gravitational field strength at distance r from a point mass.
Gravitational potential in a radial field (zero at infinity).
The restoring force of a spring is proportional to extension.
Acceleration in simple harmonic motion is proportional to displacement.
Period of oscillation for a mass on a spring.
Angular momentum equals moment of inertia times angular velocity.
Final velocity after uniform acceleration.
Displacement under uniform acceleration.
Links velocities, acceleration and displacement without time.
Acceleration directed towards the centre of a circular path.
Net force required for circular motion.
Ratio of tensile stress to tensile strain.
Fractional change in length under load.
Energy stored in a stretched material within the elastic limit.
Charges, currents, and electric and magnetic fields.
Power dissipated equals voltage times current.
Capacitance is charge stored per unit voltage.
Resistance of a wire depends on resistivity, length and area.
Energy stored in a charged capacitor.
Exponential decay of charge on a discharging capacitor.
The electrostatic force between two charges follows an inverse-square law.
Electric field strength at distance r from a point charge.
Electric potential at distance r from a point charge.
The force on a charge moving through electric and magnetic fields.
A changing magnetic flux induces an electromotive force.
Flux is the magnetic field passing through an area.
Force on a current-carrying conductor in a magnetic field.
Heat, temperature, entropy and energy transfer.
Relates pressure, volume, amount and temperature of an ideal gas.
Ideal gas law in terms of particle number and Boltzmann constant.
The change in internal energy equals heat added minus work done.
Entropy change for a reversible heat transfer.
Entropy is proportional to the logarithm of the number of microstates.
Heat absorbed equals heat capacity times temperature change.
Energy to raise temperature depends on mass and specific heat capacity.
Energy absorbed or released during a change of state.
Average translational kinetic energy per molecule of an ideal gas.
Power radiated by a black body is proportional to T⁴.
Wavelength of peak emission is inversely proportional to temperature.
Oscillations and the propagation of disturbances.
Wave speed equals frequency times wavelength.
The behaviour and properties of light.
Describes how light bends when passing between media of different index.
Critical angle for total internal reflection in an optically denser medium.
Condition for constructive interference from a diffraction grating.
Relates object distance, image distance and focal length.
Physics at the smallest scales, where action is quantised.
The energy of a photon is proportional to its frequency.
The kinetic energy of emitted electrons depends on photon frequency.
Matter has a wavelength inversely proportional to momentum.
Number of undecayed nuclei decreases exponentially with time.
Activity is the product of decay constant and number of nuclei.
Links decay constant to half-life.
Space, time and gravity at high speeds and large scales.
Mass and energy are equivalent and interconvertible.
Quantifies time dilation and length contraction at speed v.
Recession velocity of a galaxy is proportional to its distance.