Energy-Momentum Relation

E^2 = (pc)^2 + (mc^2)^2

Relates energy, momentum, and mass. For massless particles (photons): E = pc.

Variables

Total energy

Momentum

kg·m/s

Rest mass

Allowed values: greater than 0

Speed of light

Allowed values: greater than 0

m/s

Your notes

0/5000

Constants in this formula

Speed of Light in Vacuum

299,792,458. Exact by definition.

m/s

Other modern physics formulas with the same quantities

Relativistic Total Energy (Special Relativity) shares Total energy, Rest mass, Speed of light
Relativistic Kinetic Energy (Special Relativity) shares Rest mass, Speed of light
Lorentz Factor (Special Relativity) shares Speed of light
Time Dilation (Special Relativity) shares Speed of light
Length Contraction (Special Relativity) shares Speed of light
Relativistic Velocity Addition (Special Relativity) shares Speed of light

Where this formula is listed

Modern Physics formulas, under Special Relativity, alongside Relativistic Doppler Effect, Proper Time and Relativity of Simultaneity.
In the modern physics list it comes after Relativistic Kinetic Energy and before Relativistic Velocity Addition.
Modern Physics formula sheet, one of 41 formulas printed with symbol keys and SI units.
The full formula index, grouped by category and topic.

Common questions

What is the Energy-Momentum Relation formula?

Energy-Momentum Relation is written E² = (pc)² + (mc²)². Relates energy, momentum, and mass. For massless particles (photons): E = pc. It belongs to Modern Physics, under Special Relativity.

What are the units in E² = (pc)² + (mc²)²?

In SI units, E is total energy, measured in J; p is momentum, measured in kg·m/s; m is rest mass, measured in kg; c is speed of light, measured in m/s.