--- loncom/homework/templates/functionplotvector.problem	2011/11/26 02:12:45	1.1
+++ loncom/homework/templates/functionplotvector.problem	2012/02/28 22:42:34	1.2
@@ -6,24 +6,27 @@ $massy=2.1+$slope*$massx;
 $angle=180.*atan($slope)/$pi;
 $perp=$angle+90.;</script>
 <startouttext />
-A mass is sliding down the indicated incline with a constant velocity. Construct the free body diagram, making sure the forces are approximately proportionally correct. Leave unused vectors unattached.<br /> <endouttext />
+A mass is sliding down the indicated incline with a constant velocity. Construct the free body diagram, making sure the forces are approximately proportionally correct. Leave unused vectors unattached.<br />
+<i>You can use the red-colored vector sum tool to help you construct your diagram; check the boxes for the vectors you want included in the sum. The tool is just there to help you, its settings are not graded.</i>
+<br />
+<endouttext />
 <functionplotresponse xaxisvisible="no" xlabel="x" gridvisible="yes" ylabel="y" id="11" xmax="10" yaxisvisible="no" xmin="0" ymin="0" ymax="10" width="450" height="450">
 <functionplotelements>
 
 <backgroundplot function="$function" fixed="yes" />
 <plotobject label="Mass" x="$massx" y="$massy" />
-<plotvector label="Gravity" tailx="6" taily="1" tipx="9" tipy="1" />
-<plotvector label="KineticFriction" tailx="6" taily="2" tipx="9" tipy="2" />
-<plotvector label="StaticFriction" tailx="6" taily="3" tipx="9" tipy="3" />
-<plotvector label="NormalForce" tailx="6" taily="4" tipx="9" tipy="4" />
-
+<plotvector label="Gravity" tailx="7" taily="1" tipx="8" tipy="1" />
+<plotvector label="KineticFriction" tailx="7" taily="2" tipx="8" tipy="2" />
+<plotvector label="StaticFriction" tailx="7" taily="3" tipx="8" tipy="3" />
+<plotvector label="NormalForce" tailx="7" taily="4" tipx="8" tipy="4" />
+<drawvectorsum label="Sum" tailx="$massx" taily="$massy" vectorlist="Gravity,KineticFriction,StaticFriction,NormalForce" />
 </functionplotelements>
 <functionplotruleset>
 <functionplotvectorrule index="Grav" vector="Gravity" attachpoint="Mass" angle="270" angleerror="2" />
-<functionplotvectorrule index="Norm" vector="NormalForce" attachpoint="Mass" angle="$perp" angleerror="3" />
-<functionplotvectorrule index="KFriction" vector="KineticFriction" attachpoint="Mass" angle="$angle" angleerror="2" />
+<functionplotvectorrule index="Norm" vector="NormalForce" attachpoint="Mass" angle="$perp" angleerror="4" />
+<functionplotvectorrule index="KFriction" vector="KineticFriction" attachpoint="Mass" angle="$angle" angleerror="3" />
 <functionplotvectorrule index="SFriction" vector="StaticFriction" notattachpoint="Mass" />
-<functionplotvectorsumrule vectors="Gravity,NormalForce,KineticFriction" length="0" lengtherror="1" index="Total" />
+<functionplotvectorsumrule vectors="Gravity,NormalForce,KineticFriction" length="0" lengtherror="2" index="Total" />
 </functionplotruleset>
 <hintgroup showoncorrect="no">
     
@@ -36,6 +39,10 @@ A mass is sliding down the indicated inc
 <hintpart on="Total">
     <startouttext />What should be the net force on the mass?<endouttext />
 </hintpart>
+<hintpart on="Norm">
+    <startouttext />What should be the direction of the normal force?<endouttext />
+</hintpart>
+
 </hintgroup>
 </functionplotresponse>
 </problem>