Gfrktyl

Consider:

I need help drawing the two boxes on an inclination.

documentclass{standalone}

usepackage{tikz}



begin{document}



begin{tikzpicture}

draw (2,3) coordinate (A) - - (8,0) coordinate (B)

- - (2,0) coordinate (C) pic [draw,->] {angle};

fill[pattern=north west lines](2,-1) rectangle(9,0);

    draw(7,.2 5) node[left] {$theta$};

    end{tikzpicture}

end{document}

One way to draw the two inclined boxes is to use a scope with a rotate applied:

Code:

documentclass[border=1pt]{standalone}

usepackage{tikz}

usetikzlibrary{patterns}



begin{document}



begin{tikzpicture}

draw  (2,3) coordinate (A) 

    -- (8,0) coordinate (B)

    -- (2,0) coordinate (C) 

    -- cycle;

fill[pattern=north west lines]

    (2,-1) rectangle(8,0);

    draw(7,.2 5) node[left] {$theta$};



begin{scope}[rotate=atan((3-0)/(2-8))]

    draw  [fill=cyan!40, densely dashed] ([shift={(-0.5,0)}]A) rectangle ++(1,0.5);

    draw  [fill=red!20]                  ([shift={(-0.5,0)}]B) rectangle ++(1,0.5);

end{scope}

end{tikzpicture}

end{document}

documentclass[border = 5pt]{standalone}



usepackage{tikz}

usetikzlibrary{patterns, calc, quotes, angles}



definc{25}



begin{document}

begin{tikzpicture}



  % incline

  draw (0,0) coordinate(O) -- (180-inc : 7) coordinate(A) |- coordinate (D) ($(O)+(0,-1)$) -- cycle;

  draw[dashed] (O) -| coordinate (C) (A);

  fill[pattern = north west lines] (D) rectangle (O);



  % measures

  draw[|<->|] ($(A)+(-0.5, 0)$) -- ($(C)+(-0.5, 0)$) node[midway, left]{$h$};

  pic["$theta$", <->, draw, angle eccentricity = 1.2, angle radius = 1cm] {angle = A--O--C};





  % block

  begin{scope}[rotate=180-inc]

    draw[shift={(A)}, dashed] ($(A)+(-0.4,0)$) rectangle ++ (0.8,-0.6);

    draw (-0.4, 0) rectangle ++ (0.8,-0.6);

    draw[-latex] (0.4, -1) -- (-0.4, -1) node[above, midway]{${bf v}$};

  end{scope}

end{tikzpicture}

end{document}

Plus a little animation

documentclass[border = 5pt, tikz]{standalone}



usepackage{tikz}

usetikzlibrary{patterns, calc, quotes, angles}



begin{document}



foreach inc in {60,58,...,20,22,24,...,60}

{

  begin{tikzpicture}

    useasboundingbox (-8, -1.5) rectangle (1, 6);



    % incline

    draw (0,0) coordinate(O) -- (180-inc : 7) coordinate(A) |- coordinate (D) ($(O)+(0,-1)$) -- cycle;

    draw[dashed] (O) -| coordinate (C) (A);

    fill[pattern = north west lines] (D) rectangle (O);



    % measures

    draw[|<->|] ($(A)+(-0.5, 0)$) -- ($(C)+(-0.5, 0)$) node[midway, left]{$h$};

    pic["$theta$", <->, draw, angle eccentricity = 1.2, angle radius = 1cm] {angle = A--O--C};





    % block

    begin{scope}[rotate=180-inc]

      draw[shift={(A)}, dashed] ($(A)+(-0.4,0)$) rectangle ++ (0.8,-0.6);

      draw (-0.4, 0) rectangle ++ (0.8,-0.6);

      draw[-latex] (0.4, -1) -- (-0.4, -1) node[above, midway]{${bf v}$};

    end{scope}

  end{tikzpicture}

}

end{document}

A PSTricks solution only for fun purposes.

documentclass[pstricks,12pt]{standalone}

usepackage{pst-eucl}

begin{document}

pspicture(-1,-1)(8,5)

    psframe[fillstyle=vlines,hatchsep=1pt,linestyle=none](0,-.5)(7,0)

    pstTriangle[PointName=none,PointSymbol=none](0,0){A}(7,0){B}(0,4){C}

    pstMarkAngle{C}{B}{A}{$theta$}

    pcline(C)(B)naput[npos=-.05,labelsep=-pslinewidth,nrot=:U]{psframe(1,.5)psframe(8,0)(9,.5)pcline{->}(8.25,.75)(8.75,.75)naput[labelsep=12pt]{rput{*0}{$vec{v}$}}}

    pcline[offset=10pt]{|*-|*}(A)(C)naput{$h$}

endpspicture

end{document}

A Metapost alternative, purely for comparison. Compile this one with lualatex (or work out how to adapt it for plain MP).

documentclass[border=5mm]{standalone}

usepackage{luatex85}

usepackage{luamplib}

begin{document}

mplibtextextlabel{enable}

begin{mplibcode}

beginfig(1);

    numeric theta; theta = 19;



    path box;

    box = unitsquare shifted 1/2 left 

          xscaled 34 yscaled 21 shifted 1/2 up

          rotated -theta;



    z0 = origin;

    z3 = 288 left;

    x4 = x3 = x2; x1 = x0;

    y1 = y2 = -34;

    z4 = whatever * (z3 rotated -theta);



    draw z0--z3 dashed evenly scaled 1/2;

    draw z0--z1--z2--z4--cycle;



    draw box withcolor 2/3 red;

    draw box shifted z4 dashed withdots scaled 1/4 withcolor 2/3 red;



    path a, h, v;  

    a = fullcircle scaled 112 cutbefore (z0--z4) cutafter (z0--z3);

    h = (z3--z4) shifted 10 left;

    v = subpath (3,2) of box shifted (10 up rotated -theta);



    draw a; label.lft("$theta$", point 1/2 of a);

    drawarrow v; label.top("$v$", point 1/2 of v);

    drawdblarrow h; label.lft("$h$", point 1/2 of h);



endfig;

end{mplibcode}

end{document}

Without calculating any rotation, you can use decorations.markings with transform shape.

documentclass{standalone}

usepackage{tikz}

usetikzlibrary{patterns,   angles, quotes}

usetikzlibrary{decorations.markings, arrows.meta, positioning} 

tikzset{mynode/.style={

    inner sep=0pt,

    text width=1cm,

    minimum height=.5cm,

    transform shape, draw, anchor=south}}



begin{document}

begin{tikzpicture}[>=Stealth]

draw (2,3) coordinate (A) -- (8,0) coordinate (B) 

    -- (2,0) coordinate (C) pic ["$theta$"'above left=-4pt and 12pt, draw, ->, angle radius=28pt] {angle}  -- cycle;



path [decorate,

    decoration={

    markings,% switch on markings

    mark=at position 0 with {node[mynode, dashed]{};},

    mark=at position 1 with {node[mynode](V){};

    draw[->] ([yshift=4pt]V.north west) node[above=20pt,transform shape, midway] {$v$} -- ([yshift=4pt]V.north east);}}

    ]

    (A) -- (B);



fill[pattern=north west lines](C) rectangle ++(6,-1);



draw[<->] ([xshift=-4pt]A) -- node[left] {$h$} ([xshift=-4pt]C);

end{tikzpicture}

end{document}