 Four-force

The four-force is the proper time derivative of four-momentum. For constant rest mass and coordinate three-force $\mathbf{F}=d\mathbf{p}/dt$, its components are $K^{\mu }=\gamma (\mathbf{F}\cdot \mathbf{v}/c,\mathbf{F})$ in the convention $p^{\mu }=(E/c,\mathbf{p})$. Thus it packages the power transfer and three-force into one Lorentz-covariant vector.

In the context of physics, particularly in the theory of relativity, the term "four-force" refers to a four-vector that generalizes the concept of force to four-dimensional spacetime. The concept is crucial in understanding how forces behave in relativistic scenarios, where traditional Newtonian mechanics breaks down due to high velocities approaching the speed of light.