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Vector sum tool

    1: <problem>
    2: <script type="loncapa/perl">$slope=&random(0.5,0.8,0.1);
    3: $function="2+$slope*x";
    4: $massx=&random(3.5,6.5,0.1);
    5: $massy=2.1+$slope*$massx;
    6: $angle=180.*atan($slope)/$pi;
    7: $perp=$angle+90.;</script>
    8: <startouttext />
    9: 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 />
   10: <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>
   11: <br />
   12: <endouttext />
   13: <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">
   14: <functionplotelements>
   15: 
   16: <backgroundplot function="$function" fixed="yes" />
   17: <plotobject label="Mass" x="$massx" y="$massy" />
   18: <plotvector label="Gravity" tailx="7" taily="1" tipx="8" tipy="1" />
   19: <plotvector label="KineticFriction" tailx="7" taily="2" tipx="8" tipy="2" />
   20: <plotvector label="StaticFriction" tailx="7" taily="3" tipx="8" tipy="3" />
   21: <plotvector label="NormalForce" tailx="7" taily="4" tipx="8" tipy="4" />
   22: <drawvectorsum label="Sum" tailx="$massx" taily="$massy" vectorlist="Gravity,KineticFriction,StaticFriction,NormalForce" />
   23: </functionplotelements>
   24: <functionplotruleset>
   25: <functionplotvectorrule index="Grav" vector="Gravity" attachpoint="Mass" angle="270" angleerror="2" />
   26: <functionplotvectorrule index="Norm" vector="NormalForce" attachpoint="Mass" angle="$perp" angleerror="4" />
   27: <functionplotvectorrule index="KFriction" vector="KineticFriction" attachpoint="Mass" angle="$angle" angleerror="3" />
   28: <functionplotvectorrule index="SFriction" vector="StaticFriction" notattachpoint="Mass" />
   29: <functionplotvectorsumrule vectors="Gravity,NormalForce,KineticFriction" length="0" lengtherror="2" index="Total" />
   30: </functionplotruleset>
   31: <hintgroup showoncorrect="no">
   32:     
   33: <hintpart on="Grav">
   34:     <startouttext />Gravity acts on the mass and points straight down.<endouttext />
   35: </hintpart>
   36: <hintpart on="SFriction">
   37:     <startouttext />The mass is sliding.<endouttext />
   38: </hintpart>
   39: <hintpart on="Total">
   40:     <startouttext />What should be the net force on the mass?<endouttext />
   41: </hintpart>
   42: <hintpart on="Norm">
   43:     <startouttext />What should be the direction of the normal force?<endouttext />
   44: </hintpart>
   45: 
   46: </hintgroup>
   47: </functionplotresponse>
   48: </problem>