relativistic momentum

Relativistic momentum is the momentum of an object, taking relativity into account. It is not relativistically-invariant.

The term mass (i.e., with no qualifying adjective) has come to be used two ways in light of relativity: to mean the object's rest mass, which is the mass as we normally think of it (and is a recommended usage for the term mass), or to mean a relativistic mass, the mass equivalent of the object's total energy, including kinetic energy and relativistic effects. (Effectively, this potential terminology-confusion only arises due to relativity, and the difference is only for a moving object, and significant only if at relativistic speeds.)

Formulas for momentum:

(non-relativistic) momentum = MrestV

relativistic momentum = γMrestV

or given Mrel = γMrest,
relativistic momentum = MrelV

• M_rest - rest mass.
• M_rel - total mass including the rest mass, and the mass-equivalent of kinetic energy including relativistic effects.
• γ - Lorentz factor: (1-V²/C²)^-½
• V - speed of the object.
• C - speed of light in a vacuum.

(The above inclusion of the Lorentz factor accounts for special relativity, but does not fully account for general relativity.)