3 We'll start with some automatically numbered problems \ldots
6 A problem \Part{a} with \Part{b} parts.
9 \Part{a} A solution with \ans{answers}.
13 What is $5\U{Hz}$ times $10^{-3}\U{m}$?
16 \Part{a} Another solution.
17 \Part{b} this time with numbers:
18 $5\U{Hz}\cdot10^{-3}\U{m} = \ans{5\E{-3}\U{m/s}}$.
21 \ldots and move on to an explicitly numered problem.
24 An apparently difficult problem.
27 But still easily solved.
31 The last problem: draw the direction of any forces.
33 % this is a bit tricky, since we have one drawing that we'd like to show
34 % for nosolutions (just the charges), and another we would like to show
35 % when solutions are on that is very similar (charges+forces).
36 % the parts of the drawing common to both get defined as a macro:
37 \newcommand{\problemOneOhOneBaseFigure}{
38 \coordinate (A) at ($ (0,0) + 0.5*(rand,rand) $);
39 \coordinate (B) at ($ (3,1) + 0.5*(rand,rand) $);
40 \fill[red] (A) circle (6pt);
41 \fill[blue] (B) circle (3pt);
42 \node at (A) [below=8pt] {A};
43 \node at (B) [below=8pt] {B};
49 \problemOneOhOneBaseFigure{}
57 \problemOneOhOneBaseFigure{}
58 \begin{pgfonlayer}{background}
59 \draw[->] (A) -- ($ (A) ! -0.3 ! (B) $) node[pos=1,left=8pt] {\vbox{\hbox{$F_{BA}$}\hbox{($B$ on $A$)}}};
60 \draw[->] (B) -- ($ (B) ! -0.3 ! (A) $) node[pos=1,right=8pt] {\vbox{\hbox{$F_{AB}$}\hbox{($A$ on $B$)}}};
66 Note that the problem-separating space occurs after the nosolution
67 section in nosolution mode.