答案1
\documentclass[tikz,border=3.14mm]{standalone}
\begin{document}
\begin{tikzpicture}[thick]
\draw (0,0) -- (5,0);
\foreach \Y [count=\X starting from 0] in {2,-1,-1,1,-2}
{\draw[-latex] (\X,0) node[below left]{\X} (\X,{-0.1*sign(\Y)}) -- (\X,\Y)
node[anchor={sign(\Y)*(-90)}]{$F_{\X}$};}
\end{tikzpicture}
\end{document}