# Force seen by an observer traveling near the speed of light

Suppose there is a wind with velocity $v \ll c$, which is blowing on a person who is moving at velocity $u \ll c$ (both in the $x$-direction). In the rest frame of the person, the wind exerts a force $F$ on the person, where $F$ is proportional to $(v-u)^2$.

Now, say there is an observer moving in the $x$-direction at velocity $w$, which is close to the speed of light. Is there a difference in the force that the observer sees, or is it the same as in the rest frame of the person?

• I've put your math into MathJax (that is essentially LaTeX math-mode) so that I could use a proper $\ll$ comparison operator. Sep 26 '17 at 5:15
• $\:F'=F\:$ but $\:F'\ne \text{ proportional } \left(v'-u'\right)^{2}$. Sep 26 '17 at 7:45