Conceptual Physics (12th Edition)

Find $\gamma$ at v = 0.99c. It is $\frac{1}{\sqrt{1-v^{2}/c^{2}}}$, or $\frac{1}{\sqrt{1-0.99^{2}}}$, which is 7.09. The relativistic formula for momentum, $p = \gamma mv$, is greater than the classical formula $p = mv$. The momentum of the bus and the electron, when they move at 0.99c, is 7.09 times greater than predicted by classical physics.