Different cases of the angle between the velocity and acceleration vectors.
Also see other figures under the “vectors” tag: vector sum rule, right-hand rule, scalar production, or the divergence and curl of vector fields.
Edit and compile if you like:
% Author: Izaak Neutelings (October 2020) \documentclass[border=3pt,tikz]{standalone} \usepackage{physics} \usepackage{tikz} \usetikzlibrary{angles,quotes} % for pic \tikzset{>=latex} % for LaTeX arrow head \colorlet{myred}{red!65!black} \colorlet{xcol}{blue!70!black} \colorlet{vcol}{green!70!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{vvec}=[->,vcol,very thick,line cap=round] \tikzstyle{avec}=[->,acol,very thick,line cap=round] \begin{document} % POSITIVE ACCELERATION \def\v{1.6} % velocity magnitude \def\a{0.8} % acceleration magnitude \def\ang{30} % angle \begin{tikzpicture} \coordinate (O) at (0,0); \coordinate (V) at (\ang:\v); \coordinate (A) at (\ang:\a); \draw[vvec] (O)++(\ang-90:0.1) --++ (V) node[above=2,right=-2] {$\vb{v}$}; \draw[avec] (O)++(\ang+90:0.1) --++ (A) node[above=0] {$\vb{a}$}; \end{tikzpicture} % NEGATIVE ACCELERATION \begin{tikzpicture} \coordinate (O) at (0,0); \coordinate (V) at (\ang:\v); \coordinate (A) at (\ang:\a); \draw[vvec] (O)++(\ang-90:0.1) --++ (V) node[above=2,right=-2] {$\vb{v}$}; \draw[avec] (A)++(\ang+90:0.1) --++ (\ang-180:\a) node[left=-1] {$\vb{a}$}; \end{tikzpicture} % ANGLED ACCELERATION \begin{tikzpicture} \coordinate (O) at (0,0); \coordinate (V) at (10:\v); \coordinate (A) at (60:\a); \draw[vvec] (O) --++ (V) node[right=-2] {$\vb{v}$}; \draw[avec] (O) --++ (A) node[left=2] {$\vb{a}$}; \draw pic["$\theta$",draw=black,angle radius=14,angle eccentricity=1.4] {angle=V--O--A}; \end{tikzpicture} % ANGLED ACCELERATION - break down \begin{tikzpicture} \def\v{1.6} % velocity magnitude \def\a{1.1} % acceleration magnitude \def\angv{10} % angle velocity \def\anga{45} % angle acceleration \coordinate (O) at (0,0); \coordinate (V) at (\angv:\v); \coordinate (A) at (\anga:\a); \coordinate (AT) at (\angv:{\a*cos(\anga-\angv)}); \coordinate (AC) at (\angv+90:{\a*sin(\anga-\angv)}); \draw[vvec] (O)++(\angv-90:0.2) --++ (V) node[right=-2] {$\vb{v}$}; \draw[dashed] (AT) -- (A) -- (AC); \draw[avec,acol!80!black!50] (O) -- (AT) node[above=1,right=-2] {$\vb{a}_\mathrm{t}$}; \draw[avec,acol!80!black!50] (O) -- (AC) node[left=-2] {$\vb{a}_\mathrm{c}$}; \draw[avec] (O) --++ (A) node[above left=-2] {$\vb{a}$}; \draw pic["$\theta$",draw=black,angle radius=14,angle eccentricity=1.4] {angle=V--O--A}; \end{tikzpicture} % ANGLED ACCELERATION - opposite \begin{tikzpicture} \coordinate (O) at (0,0); \coordinate (V) at (10:\v); \coordinate (A) at (160:\a); \draw[dashed] (O) --++ (-170:0.4*\v); \draw[vvec] (O) --++ (V) node[right=-2] {$\vb{v}$}; \draw[avec] (O) --++ (A) node[left=2] {$\vb{a}$}; \draw pic["$\theta$",draw=black,angle radius=9,angle eccentricity=1.65] {angle=V--O--A}; \end{tikzpicture} % POSITIVE ANGULAR ACCELERATION \begin{tikzpicture} \coordinate (O) at (0,0); \coordinate (V) at (\ang:\v); \coordinate (A) at (\ang:\a); \draw[vvec] (O)++(\ang-90:0.1) --++ (V) node[above=2,right=-2] {$\vb*{\omega}$}; \draw[avec] (O)++(\ang+90:0.1) --++ (A) node[above=0] {$\vb*{\alpha}$}; \end{tikzpicture} % NEGATIVE ANGULAR ACCELERATION \begin{tikzpicture} \coordinate (O) at (0,0); \coordinate (V) at (\ang:\v); \coordinate (A) at (\ang:\a); \draw[vvec] (O)++(\ang-90:0.1) --++ (V) node[above=2,right=-2] {$\vb*{\omega}$}; \draw[avec] (A)++(\ang+90:0.1) --++ (\ang-180:\a) node[left=-1] {$\vb*{\alpha}$}; \end{tikzpicture} % ANGLED ANGULAR ACCELERATION \begin{tikzpicture} \coordinate (O) at (0,0); \coordinate (V) at (10:\v); \coordinate (A) at (60:\a); \draw[vvec] (O) --++ (V) node[right=-2] {$\vb*{\omega}$}; \draw[avec] (O) --++ (A) node[left=2] {$\vb*{\alpha}$}; \draw pic["$\theta$",draw=black,angle radius=14,angle eccentricity=1.4] {angle=V--O--A}; \end{tikzpicture} \end{document}
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