If I could turn back time

Newton's law states $F = m\ddot{r}(t)$. Solving this equation for a given force field yields a curve $r(t)$ that governs the motion of particles in that field.

The physics in a field is said to obey time-reversal symmetry if whenever $r(t)$ is a permissible motion, $r(-t)$ is as well.

Of the following forces, which does not obey time-reversal symmetry?

• Gravitational $\displaystyle F = -G\frac{Mm}{r(t)^2}\hat{r}$
• Electric $\displaystyle F = q\vec{E}$
• Magnetic $\displaystyle F = q\vec{v}(t)\times\vec{B}$

Assumptions

• Take the fields in question to be constant, and time-independent.