Per la bilancia ti propongo questa versione.
`
\documentclass{article}
\usepackage[dvipsnames]{xcolor}
\usepackage{tikz,subfig}
\usetikzlibrary{shapes,shapes.geometric,shadings}
\tikzset{riempi v/.style={left color=gray,right color=gray, middle color=lightgray}, % elementi verticali
riempi h/.style={top color=gray,bottom color=gray, middle color=lightgray} % elementi orizzontali
}
\begin{document}
\begin{tikzpicture}[font=\small,x=5mm, y=5mm, scale=.75]
\begin{scope}[draw=darkgray]
\filldraw[riempi h] (0,0) rectangle (4,1);
\filldraw[riempi h,rounded corners=2] (1,1.1)rectangle (3,1.6);
\filldraw[riempi v] (1.8,1.7) rectangle (2.3,8);
\filldraw[riempi h,rounded corners=2] (1.5,8.1)rectangle (2.6,8.6);
\filldraw[riempi h] (-4,8.7) rectangle (8,9.1);
\filldraw[rounded corners=2,riempi v] (1.8,8.8)rectangle (2.3,9.8);
\node[name=c1,shape=semicircle,shape border rotate=180, inner sep=3.75mm,draw=darkgray,ball color=lightgray,shading angle=120] at (-4,3)
{};
\node (a) at (-4,8.7) {};
\draw (a.center)–(c1.arc start);
\draw (a.center)–(c1.arc end);
\node[name=c2,shape=semicircle,shape border rotate=180, inner sep=3.75mm,draw=darkgray,ball color=lightgray,shading angle=120] at (8,3)
{};
\node (b) at (8,8.7) {};
\draw (b.center)–(c2.arc start);
\draw (b.center)–(c2.arc end);
\fill[fill=BrickRed](-5,4) rectangle (-3,5);
\fill[fill=BrickRed](7,4) rectangle (8,5);
\filldraw[fill=white] (8.1,4) rectangle (9.5,5.1);
\filldraw[fill=white] (8.4,5.1) rectangle (9.2,5.4);
\node () at (8.8,4.5) {$1$kg};
\end{scope}
\end{tikzpicture}
\end{document}
`