Fixed trajectory plot in Young and Freedman v12 p21.86 solution.

diff --git a/latex/problems/Young_and_Freedman_12/problem21.86.tex b/latex/problems/Young_and_Freedman_12/problem21.86.tex
index 515955ea46389a2b7548d3d1e46fab24b2d25445..79333498307ff1e4af552eead74d2716f36dd453 100644 (file)
--- a/latex/problems/Young_and_Freedman_12/problem21.86.tex
+++ b/latex/problems/Young_and_Freedman_12/problem21.86.tex
@@ -18,8 +18,8 @@ import Mechanics;
 import ElectroMag;
 
 real u = 1cm;
-real L = 3;
-real dy = 1;
+real L = 5;
+real dy = 2;
 int n=3;
 
 Charge q = aCharge((0,0)*u, q=1, L="$q$");
@@ -27,26 +27,29 @@ Vector v = Velocity(q.center, L="$v$");
 Wire top_plate = Wire((0,0.5*dy)*u, (L,.5*dy)*u);
 Wire bottom_plate = Wire((0,-.5*dy)*u, (L,-.5*dy)*u);
 
-path p = q.center;
-real x;
-real y;
-for (int i=0; i<=100; i+= 1) {
-  x = q.center.x+L*i/n;
-  y = q.center.y+.4*dy*(x/L)**2;
-  p = p..((x,y)*u);
-}
-draw(p, grey);
-
 Vector E;
 for (int i=0; i<n; i+=1) { 
-  E = EField((L*(i+.5)/n, -.4*dy)*u, mag=.8*dy*u, dir=90, L="$E$");
+  E = EField((L*(i+.5)/n, -.35*dy)*u, mag=.7*dy*u, dir=90, L="$E$");
   E.draw();
 }
 
+path p = q.center;
+real x, y, frac;
+int m = 20;
+for (int i=0; i<=m; i+= 1) {
+  frac = i/m;
+  x = L*frac;
+  y = 0.4*dy*frac**2;
+  p = p..(q.center + (x,y)*u);
+}
+draw(p, grey);
+
 top_plate.draw();
 bottom_plate.draw();
 v.draw();
 q.draw();
+
+draw_ijhat(q.center - (1,0)*u);
 \end{asy}
 \end{center}
 From the forces on the drop in each direction
@@ -70,6 +73,6 @@ equation for $y(t)$,
   \Delta y &= \frac{qE}{2m} \Delta t^2 \\
   q &= \frac{2m \Delta y}{E \Delta t^2}
     = \frac{2\cdot1.4\E{-11}\U{kg}\cdot3.0\E{-4}\U{m}}{8.0\E{4}\U{N/C}\cdot(1\E{-3}\U{s})^2}
-    = \ans{1.05\E{-13}\U{C}}
+    = \ans{1.0\E{-13}\U{C}} \;.
 \end{align}
 \end{solution}