% Author: Izaak Neutelings (October 2020)
% Inspiration: https://tex.stackexchange.com/questions/25531/adding-underbrace-in-tikz
\documentclass[border=3pt,tikz]{standalone}
\usepackage{physics}
\usepackage{siunitx}
\usepackage{ifthen}
\usepackage{tikz}
\usepackage[outline]{contour} % glow around text
\usetikzlibrary{calc}
\usetikzlibrary{angles,quotes} % for pic
\usetikzlibrary{patterns}
\tikzset{>=latex} % for LaTeX arrow head
\contourlength{1.4pt}

\colorlet{xcol}{blue!70!black}
\colorlet{vcol}{green!60!black}
\colorlet{myred}{red!65!black}
\colorlet{acol}{red!50!blue!80!black!80}
\tikzstyle{mass}=[line width=0.6,red!30!black,fill=red!40!black!10,rounded corners=1,
                  top color=red!40!black!20,bottom color=red!40!black!10,shading angle=20]
\tikzstyle{velocity}=[->,vcol,very thick,line cap=round]
\tikzstyle{ground}=[preaction={fill,top color=blue!70!black!10,bottom color=blue!70!black!5,shading angle=20},
                    fill,pattern color=blue!30!black,pattern=north east lines,draw=none,minimum width=0.3,minimum height=0.6]
\tikzstyle{limb}=[thick,line cap=round]

\begin{document}


% MAN ON ICE - at rest
\def\W{5.2}     % ground width
\def\L{3.2}     % length
\def\T{0.08}    % plank thickness
\def\H{2.2}     % human height
\begin{tikzpicture}
  \def\x{-0.1*\W} % human position
  \coordinate (O) at (0,0);
  
  % GROUND + PLANK
  \draw[ground] (-\W/2,0) rectangle++ (\W,-0.2);
  \draw[thick,blue!30!black] (-\W/2,0) --++ (\W,0);
  \draw[thin,brown!40!black,fill=brown!80!black,rounded corners=0.5]
    (-0.32*\L,0) --++ (\L,0) |-++ (-\L,\T) -- cycle;
  \fill[myred!80!black] (-0.08*\L,0.37*\H) circle(0.08) node[right=2,scale=0.9] {CM};
  
  % PERSON
  \draw[thick] (\x,\H) circle(0.3) coordinate (H);
  \draw[thick] (H)++(-90:0.3) coordinate (N) to[out=-92,in=92]++ (0,-0.40*\H) coordinate (P);
  \draw[limb] (N)++(-95:0.03) to[out=-105,in=90]++ (-0.02*\W,-0.4*\H);
  \draw[limb] (N)++(-85:0.03) to[out=-80,in=90]++ (0.02*\W,-0.4*\H);
  \draw[limb] (P) to[out=-92,in=82] (\x-0.02*\W,\T);
  \draw[limb] (P) to[out=-80,in=90] (\x+0.02*\W,\T);
  
\end{tikzpicture}


% MAN ON ICE - walking
\begin{tikzpicture}
  \def\x{-0.025*\W} % human position
  \coordinate (O) at (0,0);
  
  % GROUND + PLANK
  \draw[ground] (-\W/2,0) rectangle++ (\W,-0.2);
  \draw[thick,blue!30!black] (-\W/2,0) --++ (\W,0);
  \draw[thin,brown!40!black,fill=brown!80!black,rounded corners=0.5]
    (-0.65*\L,0) --++ (\L,0) |-++ (-\L,\T) -- cycle;
  \fill[myred!80!black] (-0.08*\L,0.37*\H) circle(0.08); %node[above=2,left=2,scale=0.9] {CM};
  
  % PERSON
  \draw[thick] (\x,\H) circle(0.3) coordinate (H);
  \draw[thick] (H)++(-90:0.3) coordinate (N) to[out=-92,in=92]++ (0,-0.40*\H) coordinate (P);
  \draw[limb] (N)++(-95:0.03) to[out=-100,in=85]++ (-0.03*\W,-0.40*\H);
  \draw[limb] (N)++(-85:0.03) to[out=-80,in=120]++ (0.04*\W,-0.38*\H);
  \draw[limb] (P) to[out=-87,in=68] (\x-0.04*\W,\T);
  \draw[limb] (P) to[out=-78,in=82] (\x+0.02*\W,\T);
  
  % VECTORS
  \draw[velocity] (\x+0.08*\W,0.52*\H) --++ (0.08*\W,0) node[right=-2] {$\vb{v}_\mathrm{h}$};
  \draw[velocity] (\x-0.18*\W,0.11*\H) --++ (-0.16*\W,0) node[above=1,left=-2] {$\vb{v}_\mathrm{p}$};
  \draw[velocity,myred] (\x+0.08*\W,0.32*\H) --++ (0.2*\W,0) node[right=-2] {$\vb{p}_\mathrm{B}$};
  \draw[velocity,myred] (\x-0.18*\W,0.32*\H) --++ (-0.2*\W,0) node[above=2,left=-2] {$\vb{p}_\mathrm{B}$};
  
\end{tikzpicture}



\end{document}