Relativistic Mass

Relativistic mass

The relativistic mass is the sum total quantity of energy in a body or system (divided by c). Thus, the mass in the formula$${\displaystyle E=m_{\text{rel}}c^{2}}$$ is the relativistic mass. For a particle of non-zero rest mass m moving at a speed ${\displaystyle v}$ relative to the observer, one finds $${\displaystyle m_{\text{rel}}={\frac {m}{\sqrt {1-{\dfrac {v^{2}}{c^{2}}}}}}.}$$