\documentclass[crop,border=5,tikz,convert={outext=.svg,command=\unexpanded{pdf2svg
    \infile\space\outfile}},multi=false]{standalone}
\usetikzlibrary{math,calc,through,shapes,patterns}

\newcommand{\markangle}[6][0.25]{
  \begin{scope}
    \clip (#2)--(#3)--(#4);
    \node (ANG) [draw, circle, minimum size=#5] at (#3){};
  \end{scope}
  \coordinate (E1) at (intersection 0 of ANG and #3--#2);
  \coordinate (E2) at (intersection 0 of ANG and #3--#4);
  %\draw[thick] (E1) to [bend right=50] (E2);
  \coordinate (EM) at ($ (E1)!0.5!(E2) $);
  \coordinate (EM) at ($ (EM)!#1!(#3) $);
  \node at (EM) {#6};
}


\def\myt{40}

\begin{document}
\begin{tikzpicture}[>=latex,scale=1]
  \fill[white] (-3,0) rectangle (3,2.3);
  \fill[gray!70] (-3,-0.75) rectangle (3,0);
%  \fill[pattern = north east lines] (-4,-0.5) rectangle (4,0);
  \draw[thick, dashed] (0,-0.55) -- (0,1.9);
  \coordinate (A) at (180-\myt:3);
  \coordinate (B) at (\myt:3);
  \coordinate (O) at (0,0);
  \coordinate (L) at (0,2);
  \coordinate (K1) at (180-\myt:2.5);
  \coordinate (K2) at (\myt:1);

  \draw[blue, ultra thick] (A) -- (O) --  (B);
  \markangle{A}{O}{L}{38}{\tiny $\alpha$}
  \markangle{L}{O}{B}{41}{\tiny $\alpha'$}
  \markangle{0,-0.5}{O}{3,0}{16}{$\cdot$}
  \coordinate (K1e) at ($ (K1)!0.6!(O) $);
  \draw[dotted] (K1)rectangle (K1e);
  \draw[thick,red,->] (K1) -- (K1e) node[above right] {$\vec v$};;
  \draw[thick,red,->] (K1) -- ($(K1 -| K1e)$) node[above] {$\vec v_x$};
  \draw[thick,red,->] (K1) -- ($(K1 |- K1e)$) node[below] {$\vec v_y$};

  \coordinate (K2e) at ($ (K2)!-1.5!(O) $);
  \draw[dotted] (K2)rectangle (K2e);
  \draw[thick,red,->] (K2) -- (K2e) node[below right] {$\vec v$};;
  \draw[thick,red,->] (K2) -- ($(K2 -| K2e)$) node[below] {$\vec v_x$};
  \draw[thick,red,->] (K2) -- ($(K2 |- K2e)$) node[above] {$-\vec v_y$};
  \fill[black] (K1) circle (1mm);
  \fill[black] (K2) circle (1mm);
\end{tikzpicture}


\def\myalpha{50}
\def\myn{1.8}
\tikzmath{\mybeta = asin(sin(\myalpha)/\myn);}

\begin{tikzpicture}[>=latex,scale=1]
  \fill[white] (-3,0) rectangle (3,2.5);
  \fill[gray!70] (-3,-4) rectangle (3,0);
  %\node () at (1,1){\mybeta};
  %\fill[pattern = north east lines] (-4,-0.5) rectangle (4,0);
  \draw[thick, dashed] (0,-2.5) -- (0,2.5);
  \coordinate (A) at (90+\myalpha:3);
  \coordinate (B) at (90-\myalpha:3);
  \coordinate (C) at (-90+\mybeta:4.3);
  \coordinate (O) at (0,0);
  \coordinate (L) at (0,2);
  \coordinate (K1) at (90+\myalpha:2.5);
  \coordinate (K2) at (-90+\mybeta:1.4);

  \draw[blue, ultra thick] (A) -- (O) --  (C);
  \markangle{A}{O}{L}{40}{\tiny $\alpha$}
  \markangle{0,-3}{O}{C}{55}{\tiny $\beta$}
  \markangle{0,-1}{O}{-3,0}{18}{$\cdot$}
  \node () at (2,0.5){$n_1$};
  \node[red] () at (-1.5,-2){\footnotesize $v_2 > v_1$};
  \node () at (2,-0.5){$n_2$};

  \def\myv1{1.5}
  %\coordinate (K1) at (K2);
  \coordinate (K1e) at ($ (K1) + (-90+\myalpha:\myv1) $);
  \draw[dotted] (K1)rectangle (K1e);
  \draw[thick,red,->] (K1) -- (K1e) node[above right] {$\vec v_1$};;
  \draw[thick,red,->] (K1) -- ($(K1 -| K1e)$) node[above] {$\vec v_{x}$};
  \draw[thick,red,->] (K1) -- ($(K1 |- K1e)$) node[below] {$\vec v_{1y}$};

  \tikzmath{\myv2 = \myv1*sin(\myalpha)/sin(\mybeta);}
  \coordinate (K2e) at  ($ (K2) + (-90+\mybeta:\myv2) $);
  \draw[dotted] (K2)rectangle (K2e);
  \draw[thick,red,->] (K2) -- (K2e) node[above right] {$\vec v_2$};;
  \draw[thick,red,->] (K2) -- ($(K2 -| K2e)$) node[above] {$\vec v_{x}$};
  \draw[thick,red,->] (K2) -- ($(K2 |- K2e)$) node[left] {$\vec v_{2y}$};

  \draw[thick,black!50!green,->] (K1) -++ (0.5,0);
  \draw[thick,black!50!green,->] (K1) -++ (-0.5,0);
  \draw[thick,black!50!green,->] (K1) -++ (0,0.5) node[right] {$F_1$};
  \draw[thick,black!50!green,->] (K1) -++ (0,-0.5);

  \draw[thick,black!50!green,->] (K2) -++ (0.9,0) node[below] {$F_2$};
  \draw[thick,black!50!green,->] (K2) -++ (-0.9,0);
  \draw[thick,black!50!green,->] (K2) -++ (0,0.9);
  \draw[thick,black!50!green,->] (K2) -++ (0,-0.9);

  \draw[thick,black!50!green,->] (O) -++ (0.7,0);
  \draw[thick,black!50!green,->] (O) -++ (-0.7,0);
  \draw[ultra thick,black!50!green,->] (O) -++ (0,0.5) node[right] {$F_1$};
  \draw[ultra thick,black!50!green,->] (O) -++ (0,-0.9) node[left] {$F_2$};

  \fill[black] (K1) circle (1mm);
  \fill[black] (K2) circle (1mm);
  \fill[black] (O) circle (1mm);
\end{tikzpicture}
\end{document}