画斜面

Question

我正在尝试画这个东西：

这是我目前所做的（我的图片略有不同，但对我的目的来说没问题）

\begin{tikzpicture}
            
    \coordinate (a) at (3.5,0.35);
    \coordinate (b) at (3.5,1.75);
    \coordinate (c) at (2.95,1.5);
            
    \draw[line width=0.6mm] (0,0) -- (8,0) -- (8,4) -- cycle;
    \draw[line width=0.6mm,-stealth,blue,rotate=26.57] (-1,0) -- (10,0);
    \draw[line width=0.6mm,black,rotate=26.57,fill=lightgray] (3.1305,0.05) rectangle (5.1305,1.05);
            
    \draw[line width=0.6mm,-stealth, red] (3.5,2.35) -- (3.5,0.35);
    \draw[line width=0.6mm,-stealth, red,rotate=26.57] (4.2,0.55) -- (5.7,0.55);
    \draw[line width=0.6mm,-stealth, blue,rotate=26.57] (4.2,0.55) -- (3.3,0.55);
    \draw[line width=0.3mm,dashed, blue,rotate=26.57] (3.3,0.55) -- (3.3,-1);
    \draw[line width=0.6mm,-stealth, red,rotate=26.57] (4.2,0.55) -- (4.2,2.05);
            
    \node[circ,red] at (3.5,2.35){};
            
    \draw[line width=0.3mm] (1,0) arc (0:26.57:1);
            
    \pic [draw, -, line width = 0.3mm, angle eccentricity=1.5,green] {angle = b--a--c};
    \pic [draw, -, line width = 0.3mm, angle eccentricity=1.5,green] {angle = c--b--a};
            
\end{tikzpicture}

这给了我这个：

我有几个问题：

1. 有什么方法可以改变这些显示角度的圆弧的半径吗？出于某种原因，一个绿色角度没问题，但另一个太大了。这也让我把主\alpha角度画成圆弧
2. 如果没有办法改变这个圆弧半径，我该如何正常绘制我的图画呢？

我知道代码很糟糕:\