Relativistic force
= Relativistic force
{title2=$F=dp/dt$}
For three-momentum $p=\gamma mv$, force and acceleration satisfy
$$
F=m\gamma\left(a+\frac{\gamma^2}{c^2}(v\mathbin{\cdot}a)v\right),
\qquad
a=\frac1{m\gamma}\left(F-\frac{F\mathbin{\cdot}v}{c^2}v\right).
$$
The associated <four-force> uses <proper time> instead of coordinate time and is a different, four-dimensional object.