// Numbas version: exam_results_page_options {"name": "Moment of a Force: using Verignon's Theorem", "extensions": ["geogebra", "quantities"], "custom_part_types": [{"source": {"pk": 19, "author": {"name": "William Haynes", "pk": 2530}, "edit_page": "/part_type/19/edit"}, "name": "Engineering Accuracy with units", "short_name": "engineering-answer", "description": "

A value with units marked right if within an adjustable % error of the correct value.  Marked close if within a wider margin of error.

", "help_url": "", "input_widget": "string", "input_options": {"correctAnswer": "siground(settings['correctAnswer'],4)", "hint": {"static": true, "value": ""}, "allowEmpty": {"static": true, "value": true}}, "can_be_gap": true, "can_be_step": true, "marking_script": "mark:\nswitch( \n right and good_units and right_sign, add_credit(1.0,'Correct.'),\n right and good_units and not right_sign, add_credit(settings['C2'],'Wrong sign.'),\n right and right_sign and not good_units, add_credit(settings['C2'],'Correct value, but wrong or missing units.'),\n close and good_units, add_credit(settings['C1'],'Close.'),\n close and not good_units, add_credit(settings['C3'],'Answer is close, but wrong or missing units.'),\n incorrect('Wrong answer.')\n)\n\n\ninterpreted_answer:\nqty(student_scalar, student_units)\n\n\n\ncorrect_quantity:\nsettings[\"correctAnswer\"]\n\n\n\ncorrect_units:\nunits(correct_quantity)\n\n\nallowed_notation_styles:\n[\"plain\",\"en\"]\n\nmatch_student_number:\nmatchnumber(studentAnswer,allowed_notation_styles)\n\nstudent_scalar:\nmatch_student_number[1]\n\nstudent_units:\nreplace_regex('ohms','ohm',\n replace_regex('\u00b0', ' deg',\n replace_regex('-', ' ' ,\n studentAnswer[len(match_student_number[0])..len(studentAnswer)])),\"i\")\n\ngood_units:\ntry(\ncompatible(quantity(1, student_units),correct_units),\nmsg,\nfeedback(msg);false)\n\n\nstudent_quantity:\nswitch(not good_units, \n student_scalar * correct_units, \n not right_sign,\n -quantity(student_scalar, student_units),\n quantity(student_scalar,student_units)\n)\n \n\n\npercent_error:\ntry(\nscalar(abs((correct_quantity - student_quantity)/correct_quantity))*100 \n,msg,\nif(student_quantity=correct_quantity,0,100))\n \n\nright:\npercent_error <= settings['right']\n\n\nclose:\nright_sign and percent_error <= settings['close']\n\nright_sign:\nsign(student_scalar) = sign(correct_quantity)", "marking_notes": [{"name": "mark", "description": "This is the main marking note. It should award credit and provide feedback based on the student's answer.", "definition": "switch( \n right and good_units and right_sign, add_credit(1.0,'Correct.'),\n right and good_units and not right_sign, add_credit(settings['C2'],'Wrong sign.'),\n right and right_sign and not good_units, add_credit(settings['C2'],'Correct value, but wrong or missing units.'),\n close and good_units, add_credit(settings['C1'],'Close.'),\n close and not good_units, add_credit(settings['C3'],'Answer is close, but wrong or missing units.'),\n incorrect('Wrong answer.')\n)\n"}, {"name": "interpreted_answer", "description": "A value representing the student's answer to this part.", "definition": "qty(student_scalar, student_units)\n\n"}, {"name": "correct_quantity", "description": "", "definition": "settings[\"correctAnswer\"]\n\n"}, {"name": "correct_units", "description": "", "definition": "units(correct_quantity)\n"}, {"name": "allowed_notation_styles", "description": "", "definition": "[\"plain\",\"en\"]"}, {"name": "match_student_number", "description": "", "definition": "matchnumber(studentAnswer,allowed_notation_styles)"}, {"name": "student_scalar", "description": "", "definition": "match_student_number[1]"}, {"name": "student_units", "description": "

Modify the unit portion of the student's answer by

\n

1. replacing \"ohms\" with \"ohm\"  case insensitive

\n

2. replacing '-' with ' ' 

\n

3. replacing '°' with ' deg' 

\n

to allow answers like 10 ft-lb and 30°

", "definition": "replace_regex('ohms','ohm',\n replace_regex('\u00b0', ' deg',\n replace_regex('-', ' ' ,\n studentAnswer[len(match_student_number[0])..len(studentAnswer)])),\"i\")"}, {"name": "good_units", "description": "", "definition": "try(\ncompatible(quantity(1, student_units),correct_units),\nmsg,\nfeedback(msg);false)\n"}, {"name": "student_quantity", "description": "

This fixes the student answer for two common errors.  

\n

If student_units are wrong  - replace with correct units

\n

If student_scalar has the wrong sign - replace with right sign

\n

If student makes both errors, only one gets fixed.

", "definition": "switch(not good_units, \n student_scalar * correct_units, \n not right_sign,\n -quantity(student_scalar, student_units),\n quantity(student_scalar,student_units)\n)\n \n"}, {"name": "percent_error", "description": "", "definition": "try(\nscalar(abs((correct_quantity - student_quantity)/correct_quantity))*100 \n,msg,\nif(student_quantity=correct_quantity,0,100))\n "}, {"name": "right", "description": "", "definition": "percent_error <= settings['right']\n"}, {"name": "close", "description": "

Only marked close if the student actually has the right sign.

", "definition": "right_sign and percent_error <= settings['close']"}, {"name": "right_sign", "description": "", "definition": "sign(student_scalar) = sign(correct_quantity) "}], "settings": [{"name": "correctAnswer", "label": "Correct Quantity.", "help_url": "", "hint": "The correct answer given as a JME quantity.", "input_type": "code", "default_value": "", "evaluate": true}, {"name": "right", "label": "% Accuracy for right.", "help_url": "", "hint": "Question will be considered correct if the scalar part of the student's answer is within this % of correct value.", "input_type": "code", "default_value": "0.2", "evaluate": true}, {"name": "close", "label": "% Accuracy for close.", "help_url": "", "hint": "Question will be considered close if the scalar part of the student's answer is within this % of correct value.", "input_type": "code", "default_value": "1.0", "evaluate": true}, {"name": "C1", "label": "Close with units.", "help_url": "", "hint": "Partial Credit for close value with appropriate units.  if correct answer is 100 N and close is ±1%,
99  N is accepted.", "input_type": "percent", "default_value": "75"}, {"name": "C2", "label": "No units or wrong sign", "help_url": "", "hint": "Partial credit for forgetting units or using wrong sign.
If the correct answer is 100 N, both 100 and -100 N are accepted.", "input_type": "percent", "default_value": "50"}, {"name": "C3", "label": "Close, no units.", "help_url": "", "hint": "Partial Credit for close value but forgotten units.
This value would be close if the expected units were provided.  If the correct answer is 100 N, and close is ±1%,
99 is accepted.", "input_type": "percent", "default_value": "25"}], "public_availability": "always", "published": true, "extensions": ["quantities"]}], "resources": [], "navigation": {"allowregen": true, "showfrontpage": false, "preventleave": false, "typeendtoleave": false}, "question_groups": [{"pickingStrategy": "all-ordered", "questions": [{"name": "Moment of a Force: using Verignon's Theorem", "tags": ["Mechanics, statics, moments, verignon's theorem"], "metadata": {"description": "

Calculate the moment of a force about three points using Verignon' theorem.  All forces and points are in the same plane.

", "licence": "Creative Commons Attribution-NonCommercial 4.0 International"}, "statement": "

{applet}

\n

Force $\\mathbf{F}$, which has a magnitude of {F}, acts along a line passing through points $D$ and $D'$.   The grid units are in [{units[0]}] and counter-clockwise moments are positive.  Determine the moment of the force about points $A$ and $B$ using Verignon's Theorem

\n

\n

", "advice": "

Verignon's Theorem:  $M = \\pm F_x\\ d_y \\pm F_y\\ d_x$

\n

Verigon's theorem says that the moment of a force is the sum of the moments of its components.

\n

Procedure:

\n
    \n
  1. Decompose force $\\mathbf{F}$ into its $x$- and $y$-components.
  2. \n
  3. Determine the horizontal and vertical distances from the moment center to a point on the line of action of $\\mathbf{F}$.  In this problem:\n
      \n
    1. $d_x$ is the horizontal distance from $D$ or $D'$ to point $A$ or $B$.
    2. \n
    3. $d_y$ is the vertical distance from $D$ or $D'$ to $A$ or  $B$.
    4. \n
    \n
  4. \n
  5. The moments of the components are $F_x\\ d_y$ and $F_y\\ d_x$.
  6. \n
  7. The signs of these moments are determined by inspection:  positive if counter-clockwise, negative if clockwise.
  8. \n
  9. The total moment is the sum of the component moments.
  10. \n
", "rulesets": {}, "extensions": ["geogebra", "quantities"], "builtin_constants": {"e": true, "pi,\u03c0": true, "i": true}, "constants": [], "variables": {"Fy": {"name": "Fy", "group": "Ungrouped variables", "definition": "qty(force[1],units[1])", "description": "", "templateType": "anything", "can_override": false}, "test2": {"name": "test2", "group": "Inputs", "definition": "some(map(p[0]=q[0] or p[1]=q[1],[p,q],combinations([A,B,C,D,D'],2)))", "description": "

map(sqrt(x^2+y^2),[x,y],[ [3,4], [5,12] ])

", "templateType": "anything", "can_override": false}, "dir_b": {"name": "dir_b", "group": "Ungrouped variables", "definition": "if(sign(MB)>=0,1,-1)", "description": "", "templateType": "anything", "can_override": false}, "dir_c": {"name": "dir_c", "group": "Ungrouped variables", "definition": "if(sign(MC)>=0,1,-1)", "description": "", "templateType": "anything", "can_override": false}, "Fx": {"name": "Fx", "group": "Ungrouped variables", "definition": "qty(force[0],units[1])", "description": "", "templateType": "anything", "can_override": false}, "Ma": {"name": "Ma", "group": "Ungrouped variables", "definition": "qty(cross(ra,force)[2], units[0] + ' ' + units[1])\n", "description": "", "templateType": "anything", "can_override": false}, "Mc": {"name": "Mc", "group": "Ungrouped variables", "definition": "qty(cross(rc,force)[2], units[0] + ' ' + units[1])", "description": "", "templateType": "anything", "can_override": false}, "ra": {"name": "ra", "group": "Ungrouped variables", "definition": "D-A+vector(0,0,0)", "description": "

position vector

", "templateType": "anything", "can_override": false}, "units": {"name": "units", "group": "Inputs", "definition": "random(['in','lb'],['ft','lb'],['m','N'],['m','kN'])", "description": "", "templateType": "anything", "can_override": false}, "D": {"name": "D", "group": "Inputs", "definition": "vector(random(-8..8),random(-8..8))", "description": "

Point D

", "templateType": "anything", "can_override": false}, "B": {"name": "B", "group": "Inputs", "definition": "vector(random(-8..8),random(-8..8))", "description": "

point B

", "templateType": "anything", "can_override": false}, "Mb": {"name": "Mb", "group": "Ungrouped variables", "definition": "qty(cross(rb,force)[2], units[0] + ' ' + units[1])", "description": "", "templateType": "anything", "can_override": false}, "force": {"name": "force", "group": "Ungrouped variables", "definition": "scalar(F)(D'-D)/abs(D'-D) + vector(0,0,0)\n", "description": "

\n

Vector Force  = F λ

\n

λ = (D'-D)/abs(D'-D)

", "templateType": "anything", "can_override": false}, "A": {"name": "A", "group": "Inputs", "definition": "vector(random(-8..8),random(-8..8))", "description": "

point A

", "templateType": "anything", "can_override": false}, "dir_a": {"name": "dir_a", "group": "Ungrouped variables", "definition": "if(sign(MA)>=0,1,-1)", "description": "

replacement variable for direction of moment.

", "templateType": "anything", "can_override": false}, "rc": {"name": "rc", "group": "Ungrouped variables", "definition": "D-C+vector(0,0,0)\n", "description": "

position vector

", "templateType": "anything", "can_override": false}, "sum": {"name": "sum", "group": "Ungrouped variables", "definition": "Mx-My", "description": "", "templateType": "anything", "can_override": false}, "rb": {"name": "rb", "group": "Ungrouped variables", "definition": "D-B+vector(0,0,0)\n", "description": "

position vector

", "templateType": "anything", "can_override": false}, "F": {"name": "F", "group": "Inputs", "definition": "qty(random(1..5)random(1,2,5,10,20),units[1])", "description": "

Magnitude of force F

", "templateType": "anything", "can_override": false}, "debug": {"name": "debug", "group": "Inputs", "definition": "false", "description": "", "templateType": "anything", "can_override": false}, "test": {"name": "test", "group": "Inputs", "definition": "align(A,B)", "description": "", "templateType": "anything", "can_override": false}, "D'": {"name": "D'", "group": "Inputs", "definition": "vector(random(-8..8),random(-8..8))", "description": "

Point D' on loa

", "templateType": "anything", "can_override": false}, "C": {"name": "C", "group": "Inputs", "definition": "vector(random(-8..8),random(-8..8))", "description": "

point C

", "templateType": "anything", "can_override": false}, "My": {"name": "My", "group": "Ungrouped variables", "definition": "qty(\n siground(cross(ra,vector(0,force[1],0))[2],4),\n units[0] + ' ' + units[1])\n\n", "description": "", "templateType": "anything", "can_override": false}, "Mx": {"name": "Mx", "group": "Ungrouped variables", "definition": "qty(\n siground(cross(ra,vector(force[0],0,0))[2],4),\n units[0] + ' ' + units[1])\n\n", "description": "

Moment of F_x about point A

", "templateType": "anything", "can_override": false}, "applet": {"name": "applet", "group": "Ungrouped variables", "definition": "geogebra_applet('n8thnjk7', params)\n\n", "description": "", "templateType": "anything", "can_override": false}, "params": {"name": "params", "group": "Ungrouped variables", "definition": "[A: A, B: B, C: C, D: D ,D': D', F: scalar(F)]", "description": "", "templateType": "anything", "can_override": false}}, "variablesTest": {"condition": "// makes sure that no point aligns vertically or horizontally with another\nnot some(map(p[0]=q[0] or p[1]=q[1],[p,q],combinations([A,B,C,D,D'],2)))\nand sign(ma)<>sign(mb)\n", "maxRuns": 100}, "ungrouped_variables": ["ra", "rb", "rc", "force", "Mx", "My", "Ma", "Mb", "Mc", "sum", "Fx", "Fy", "dir_a", "dir_b", "dir_c", "applet", "params"], "variable_groups": [{"name": "Inputs", "variables": ["A", "B", "C", "D", "D'", "F", "units", "debug", "test", "test2"]}], "functions": {"Align": {"parameters": [["V1", "vector"], ["V2", "vector"]], "type": "boolean", "language": "jme", "definition": "(V1[0]=V2[0]) or (V1[1]=V2[1])"}}, "preamble": {"js": "", "css": ""}, "parts": [{"type": "gapfill", "useCustomName": true, "customName": "Rectangular components", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "

Determine the magnitudes of the rectangular components of $\\mathbf{F}$.

\n

$F_x$ = [[0]]  $F_y$ = [[1]]   $F_x$ = {siground(Fx,4)} $F_y$ = {siground(Fy,4)}

\n

Determine the horizontal and vertical distances from $D$ to $A$.

\n

$d_x$ = [[2]]  $d_y$ = [[3]]  Delta = {D-A}

\n

\n

\n

\n

", "gaps": [{"type": "engineering-answer", "useCustomName": true, "customName": "fx", "marks": "5", "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "settings": {"correctAnswer": "abs(Fx)", "right": "0.2", "close": "1.0", "C1": "75", "C2": "50", "C3": "25"}}, {"type": "engineering-answer", "useCustomName": true, "customName": "fy", "marks": "5", "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "settings": {"correctAnswer": "abs(Fy)", "right": "0.2", "close": "1.0", "C1": "75", "C2": "50", "C3": "25"}}, {"type": "engineering-answer", "useCustomName": true, "customName": "dx", "marks": "5", "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "settings": {"correctAnswer": "abs(qty((D-A)[0],units[0]))", "right": "0.2", "close": "1.0", "C1": "75", "C2": "50", "C3": "25"}}, {"type": "engineering-answer", "useCustomName": true, "customName": "dy", "marks": "5", "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "settings": {"correctAnswer": "abs(qty((D-A)[1],units[0]))", "right": "0.2", "close": "1.0", "C1": "75", "C2": "50", "C3": "25"}}], "sortAnswers": false}, {"type": "gapfill", "useCustomName": true, "customName": " Scalar Components of $M_A$", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "

Determine the moments of the components.  Counterclockwise moment are positive.

\n

The moment of $F_x$ about point $A$ is [[0]] = {siground(mx,4)}

\n

The moment of $F_y$ is about point $A$ is [[1]]  = {siground(my,4)}

\n

 

\n

\n

\n

", "gaps": [{"type": "engineering-answer", "useCustomName": true, "customName": "M1", "marks": "5", "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "settings": {"correctAnswer": "Mx", "right": "0.2", "close": "1.0", "C1": "75", "C2": "50", "C3": "25"}}, {"type": "engineering-answer", "useCustomName": true, "customName": "M2", "marks": "5", "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "settings": {"correctAnswer": "My", "right": "0.2", "close": "1.0", "C1": "75", "C2": "50", "C3": "25"}}], "sortAnswers": false}, {"type": "gapfill", "useCustomName": true, "customName": "$M_A$", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "

Add the moments of the components to determine the moment of force $\\mathbf{F}$ about point $A$ .   

\n

$\\mathbf{M}_A$ is a [[0]] moment with a magnitude of [[1]]

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In the same way, determine the moment of force $\\mathbf{F}$ about point $B$ .    

\n

$\\mathbf{M}_B$ is a [[0]] moment with a magnitude of [[1]]

\n

$M_b$= {siground(Mb,4)}.

", "gaps": [{"type": "1_n_2", "useCustomName": true, "customName": "Direction", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": false, "showFeedbackIcon": false, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minMarks": 0, "maxMarks": 0, "shuffleChoices": false, "displayType": "dropdownlist", "displayColumns": 0, "showCellAnswerState": true, "choices": ["Counterclockwise", "Clockwise"], "matrix": ["if(dir_b=1,5,0)", "if(dir_b=-1,5,0)"], "distractors": ["You chose Counterclockwise", "You chose Clockwise."]}, {"type": "engineering-answer", "useCustomName": true, "customName": "Mag", "marks": "5", "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "settings": {"correctAnswer": "abs(Mb)", "right": "0.2", "close": "1.0", "C1": "75", "C2": "50", "C3": "25"}}], "sortAnswers": false}], "partsMode": "all", "maxMarks": 0, "objectives": [], "penalties": [], "objectiveVisibility": "always", "penaltyVisibility": "always", "contributors": [{"name": "William Haynes", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/2530/"}]}]}], "contributors": [{"name": "William Haynes", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/2530/"}]}