Add illustration for Serway and Jewett v8's problem 23.50.

diff --git a/latex/problems/Serway_and_Jewett_8/problem23.50.tex b/latex/problems/Serway_and_Jewett_8/problem23.50.tex
index f46e040beafe92aa298f6c76779a88cf5ce509e9..a5e09c143b378ca3ab3c67d2e6b0170af5cf3eca 100644 (file)
--- a/latex/problems/Serway_and_Jewett_8/problem23.50.tex
+++ b/latex/problems/Serway_and_Jewett_8/problem23.50.tex
@@ -6,6 +6,31 @@ P23.50b, the spring stretches by $d=3.50\U{cm}$ from its original
 length and reaches a new equilibrium position with a separation
 between the charges of $r=5.00\U{cm}$.  What is the force constant of
 the spring?
+\begin{center}
+\begin{asy}
+import Mechanics;
+import ElectroMag;
+
+real u = 0.1cm;
+real ceil_width = 3u;
+real frame_space = 20u;
+real initial_stretch = 10u;
+real dx = 3.5u;
+real dab = 5u;
+
+Surface c1 = Surface(pFrom=(ceil_width,0), pTo=(-ceil_width,0));
+Charge a1 = pCharge((0, -initial_stretch), L="$q_1$");
+Spring s1 = Spring(pFrom=(0,0), pTo=a1.center);
+c1.draw(); s1.draw(); a1.draw();
+
+Surface c2 = Surface(pFrom=(frame_space+ceil_width,0),
+                    pTo=(frame_space-ceil_width,0));
+Charge a2 = pCharge((frame_space, -initial_stretch-dx));
+Charge b = nCharge(a2.center - (0, dab), L="$q_2$");
+Spring s2 = Spring(pFrom=(frame_space,0), pTo=a2.center);
+c2.draw(); s2.draw(); a2.draw(); b.draw();
+\end{asy}
+\end{center}
 \end{problem*}
 
 \begin{solution}