Relativistic kinetic energy

Definition

Relativistic kinetic energy is the kinetic energy of an object moving at a significant fraction of the speed of light. It accounts for relativistic effects predicted by Einstein's theory of special relativity.

5 Must Know Facts For Your Next Test

1. Relativistic kinetic energy is given by the equation $K = (\gamma - 1)mc^2$, where $\gamma$ is the Lorentz factor, $m$ is the rest mass, and $c$ is the speed of light.
2. As an object's velocity approaches the speed of light, its relativistic kinetic energy increases without bound.
3. At low velocities (much less than the speed of light), relativistic kinetic energy approximates classical kinetic energy, $K = \frac{1}{2}mv^2$.
4. The Lorentz factor $\gamma$ is defined as $\gamma = \frac{1}{\sqrt{1 - \frac{v^2}{c^2}}}$, where $v$ is the velocity of the object.
5. Relativistic kinetic energy includes both the increase in mass with velocity and time dilation effects.

Review Questions

• What equation defines relativistic kinetic energy?
• How does relativistic kinetic energy compare to classical kinetic energy at low velocities?
• Explain how the Lorentz factor affects relativistic kinetic energy.

Related terms

Special Relativity: A theory proposed by Einstein that describes the physics of objects moving at constant high speeds close to that of light.

Lorentz Factor: $$\gamma = \frac{1}{\sqrt{1-\frac{v^2}{c^2}}}$$, a factor that appears in several equations in special relativity and accounts for time dilation and length contraction.

Rest Mass Energy: $E_0 = mc^2$, which represents the intrinsic energy contained within an object's rest mass.