// Numbas version: finer_feedback_settings
{"name": "Equilibrium of a three-force body: triangle", "extensions": ["geogebra", "weh", "quantities"], "custom_part_types": [{"source": {"pk": 24, "author": {"name": "William Haynes", "pk": 2530}, "edit_page": "/part_type/24/edit"}, "name": "Angle quantity", "short_name": "angle-quantity-from-reference", "description": "<p>Angle&nbsp;as a quantity in degrees.</p>", "help_url": "", "input_widget": "string", "input_options": {"correctAnswer": "plain_string(settings['correct_quantity'])", "hint": {"static": true, "value": ""}, "allowEmpty": {"static": true, "value": false}}, "can_be_gap": true, "can_be_step": true, "marking_script": "mark:\nswitch( \nright and good_units and right_sign and angle_in_range, add_credit(1.0,'Correct.'),\nright and good_units and not right_sign, add_credit(settings['C2'],'Wrong sign.'),\nright and right_sign and not good_units, add_credit(settings['C2'],'Correct angle, but missing degree symbol.'),\nright and good_units and right_sign and not angle_in_range,add_credit(settings['C1'],'Angle is out of range.'),\nclose and good_units, add_credit(settings['C1'],'Close.'),\nclose and not good_units, add_credit(settings['C3'],'Answer is close, but missing degree symbol.'),\nincorrect('Wrong answer.')\n)\n\ninterpreted_answer:\nqty(student_scalar, student_units)\n\ncorrect_scalar:\nscalar(correct_quantity)\n  \n\ncorrect_quantity:\nsettings['correct_quantity']\n\ncorrect_units:\nunits(correct_quantity)\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:\njoin(\nsplit(studentAnswer[len(match_student_number[0])..len(studentAnswer)]\n,\"\u00b0\"),\" deg\")\n\n\n\ngood_units:\ntry(\nkind(quantity(1, student_units))= kind(correct_quantity),\nmsg,\nfeedback(msg);false)\n\nstudent_quantity:\nswitch(not good_units, \nstudent_scalar * correct_units, \nnot right_sign,\n-quantity(student_scalar, student_units),\nquantity(student_scalar,student_units)\n)\n\nright_sign:\nsign(student_scalar) = sign(correct_quantity)\n\nangle_in_range:\nif(settings['restrict_angle'], abs(student_scalar) <= 90, true)\n\nright:\nwithinTolerance(abs(student_scalar), abs(correct_scalar), settings['right'])\n\nclose:\nwithinTolerance(student_scalar, correct_scalar, settings['close'])", "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( \nright and good_units and right_sign and angle_in_range, add_credit(1.0,'Correct.'),\nright and good_units and not right_sign, add_credit(settings['C2'],'Wrong sign.'),\nright and right_sign and not good_units, add_credit(settings['C2'],'Correct angle, but missing degree symbol.'),\nright and good_units and right_sign and not angle_in_range,add_credit(settings['C1'],'Angle is out of range.'),\nclose and good_units, add_credit(settings['C1'],'Close.'),\nclose and not good_units, add_credit(settings['C3'],'Answer is close, but missing degree symbol.'),\nincorrect('Wrong answer.')\n)"}, {"name": "interpreted_answer", "description": "A value representing the student's answer to this part.", "definition": "qty(student_scalar, student_units)"}, {"name": "correct_scalar", "description": "", "definition": "scalar(correct_quantity)\n  "}, {"name": "correct_quantity", "description": "", "definition": "settings['correct_quantity']"}, {"name": "correct_units", "description": "", "definition": "units(correct_quantity)"}, {"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": "", "definition": "join(\nsplit(studentAnswer[len(match_student_number[0])..len(studentAnswer)]\n,\"\u00b0\"),\" deg\")\n\n"}, {"name": "good_units", "description": "", "definition": "try(\nkind(quantity(1, student_units))= kind(correct_quantity),\nmsg,\nfeedback(msg);false)"}, {"name": "student_quantity", "description": "", "definition": "switch(not good_units, \nstudent_scalar * correct_units, \nnot right_sign,\n-quantity(student_scalar, student_units),\nquantity(student_scalar,student_units)\n)"}, {"name": "right_sign", "description": "", "definition": "sign(student_scalar) = sign(correct_quantity)"}, {"name": "angle_in_range", "description": "", "definition": "if(settings['restrict_angle'], abs(student_scalar) <= 90, true)"}, {"name": "right", "description": "<p>Will check for correct sign elswhere.</p>", "definition": "withinTolerance(abs(student_scalar), abs(correct_scalar), settings['right'])"}, {"name": "close", "description": "<p>Must have correct sign to be close.</p>", "definition": "withinTolerance(student_scalar, correct_scalar, settings['close'])\n"}], "settings": [{"name": "correct_quantity", "label": "Correct Angle as quantity ", "help_url": "", "hint": "", "input_type": "code", "default_value": "qty(45,'deg')", "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 &plusmn; this amount from the correct value.", "input_type": "code", "default_value": "0.1", "evaluate": true}, {"name": "restrict_angle", "label": "Less than 90\u00b0", "help_url": "", "hint": "When checked, angle must be between -90&deg; and +90&deg;.", "input_type": "checkbox", "default_value": true}, {"name": "C1", "label": "Close with units.", "help_url": "", "hint": "Partial Credit for close value with appropriate units.", "input_type": "percent", "default_value": "75"}, {"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 &plusmn; this amount from the correct value.", "input_type": "code", "default_value": "0.5", "evaluate": true}, {"name": "C2", "label": "No units or wrong sign", "help_url": "", "hint": "Partial credit for forgetting units or using wrong sign.", "input_type": "percent", "default_value": "50"}, {"name": "C3", "label": "Close, no units.", "help_url": "", "hint": "Partial Credit for close value without units.", "input_type": "percent", "default_value": "25"}], "public_availability": "restricted", "published": false, "extensions": ["quantities"]}, {"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": "<p>A value with units marked right if within an adjustable % error of the correct value. &nbsp;Marked close if within a wider margin of error.</p>", "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": "<p>Modify&nbsp;the&nbsp;unit portion of&nbsp;the student's answer by</p>\n<p>1. replacing \"ohms\" with \"ohm\" &nbsp;case insensitive</p>\n<p>2.&nbsp;replacing '-'&nbsp;with ' '&nbsp;</p>\n<p>3. replacing '&deg;' with ' deg'&nbsp;</p>\n<p>to allow answers like 10 ft-lb and 30&deg;</p>", "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": "<p>This fixes the student answer for two common errors. &nbsp;</p>\n<p>If student_units are wrong&nbsp;&nbsp;- replace with correct units</p>\n<p>If student_scalar has the wrong sign - replace with right sign</p>\n<p>If student makes both errors, only one gets fixed.</p>", "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": "<p>Only marked close if the student actually has the right sign.</p>", "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. &nbsp;if correct answer is 100 N and close is &plusmn;1%,<br />99 &nbsp;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.<br />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.<br />This value would be close&nbsp;if the expected units were provided. &nbsp;If the correct answer is 100 N, and close is &plusmn;1%,<br />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": [{"variable_groups": [{"variables": ["theta", "units", "alpha1", "FB", "L"], "name": "Inputs"}], "statement": "<p>The triangular plate is secured by a pin at <em>A</em> and a roller at C<em>&nbsp;</em>and is&nbsp;subjected to a {FB} load as shown.</p>\n<p>Determine the reactions at the pin and the roller using the three-force body principle.&nbsp;</p>\n<p>{geogebra_applet('whu5xquv',[ ['FB',scalar(FB)] , ['L',scalar(L)], ['&theta;',radians(theta)], ['&alpha;',radians(alpha1)],['units','\"'+units[1]+'\"' ]])}</p>", "rulesets": {}, "tags": [], "ungrouped_variables": ["debug", "h", "theta_a", "alpha", "beta", "gamma", "FA", "FC"], "parts": [{"variableReplacementStrategy": "originalfirst", "unitTests": [], "marks": 0, "customMarkingAlgorithm": "", "customName": "", "prompt": "<p>A three-force body is an object acted upon by exactly three forces. &nbsp;When a three-force body is in equilibrium the lines of action of the three forces must either intersect at a common point or be parallel to each other. &nbsp;We can use this idea to find the reaction forces for&nbsp;three-force bodies.</p>\n<p>In this problem&nbsp;the lines of action of force <strong>B</strong> and force <strong>C</strong> are known and their intersection point <em>X</em> may be determined.&nbsp;</p>\n<p>Use&nbsp;the given geometric information&nbsp;to&nbsp;determine distance <em>h</em>.</p>\n<p>$h$ = [[0]]&nbsp;</p>\n<p><span data-jme-visible=\"debug\">h = {h}&nbsp;</span></p>", "showCorrectAnswer": true, "sortAnswers": false, "gaps": [{"variableReplacementStrategy": "originalfirst", "unitTests": [], "marks": "4", "customMarkingAlgorithm": "", "customName": "", "showCorrectAnswer": true, "extendBaseMarkingAlgorithm": true, "type": "engineering-answer", "useCustomName": false, "showFeedbackIcon": true, "settings": {"C2": "50", "correctAnswer": "abs(h)", "right": "0.2", "close": "1.0", "C3": "25", "C1": "75"}, "variableReplacements": [], "scripts": {}}], "extendBaseMarkingAlgorithm": true, "type": "gapfill", "useCustomName": false, "showFeedbackIcon": true, "variableReplacements": [], "scripts": {}}, {"variableReplacementStrategy": "originalfirst", "unitTests": [], "marks": 0, "customMarkingAlgorithm": "", "customName": "", "prompt": "<p>With <em>h</em> known, the direction of force <strong>A</strong> can be found since&nbsp;its&nbsp;line of action must pass through&nbsp;<em>X</em>.</p>\n<p>Use the given geometric information and determine $\\angle CAX $, which we will call $\\theta_A$</p>\n<p>$\\theta_A=$&nbsp;[[0]]</p>\n<p><span data-jme-visible=\"debug\">$\\theta_a$ = {theta_a}</span></p>", "showCorrectAnswer": true, "sortAnswers": false, "gaps": [{"variableReplacementStrategy": "originalfirst", "unitTests": [], "marks": "4", "customMarkingAlgorithm": "", "customName": "", "showCorrectAnswer": true, "extendBaseMarkingAlgorithm": true, "type": "angle-quantity-from-reference", "useCustomName": false, "showFeedbackIcon": true, "settings": {"C2": "50", "correct_quantity": "abs(theta_a)", "restrict_angle": true, "right": "0.2", "close": "1.0", "C3": "25", "C1": "75"}, "variableReplacements": [], "scripts": {}}], "extendBaseMarkingAlgorithm": true, "type": "gapfill", "useCustomName": false, "showFeedbackIcon": true, "variableReplacements": [], "scripts": {}}, {"variableReplacementStrategy": "originalfirst", "unitTests": [], "marks": 0, "customMarkingAlgorithm": "", "customName": "", "prompt": "<p>The object&nbsp;is in equilibrium so when the three forces are added tip-to-tail they form a closed triangle as shown below.</p>\n<p>Determine the three angles in the force triangle.</p>\n<p>{geogebra_applet('sckn26vg',[ ['FB',scalar(FB)] , ['L',scalar(L)], ['&theta;',radians(theta)], ['&alpha;',radians(alpha1)],['units','\"'+units[1]+'\"' ]])}</p>\n<p>$\\alpha$ = [[0]] &nbsp;$\\beta$ = [[1]]&nbsp; &nbsp;$\\gamma$ =&nbsp;[[2]]</p>\n<p><span data-jme-visible=\"debug\">$\\alpha$ = {alpha} $\\beta$ = {beta} &nbsp;$\\gamma$ = {gamma}</span></p>\n<p><span data-jme-visible=\"debug\">A = {FA} &nbsp;B = {FB} &nbsp;C = {FC}</span></p>", "showCorrectAnswer": true, "sortAnswers": false, "gaps": [{"variableReplacementStrategy": "originalfirst", "unitTests": [], "marks": "4", "customMarkingAlgorithm": "", "customName": "", "showCorrectAnswer": true, "extendBaseMarkingAlgorithm": true, "type": "angle-quantity-from-reference", "useCustomName": false, "showFeedbackIcon": true, "settings": {"C2": "50", "correct_quantity": "alpha", "restrict_angle": false, "right": "0.2", "close": "1.0", "C3": "25", "C1": "75"}, "variableReplacements": [], "scripts": {}}, {"variableReplacementStrategy": "originalfirst", "unitTests": [], "marks": "4", "customMarkingAlgorithm": "", "customName": "", "showCorrectAnswer": true, "extendBaseMarkingAlgorithm": true, "type": "angle-quantity-from-reference", "useCustomName": false, "showFeedbackIcon": true, "settings": {"C2": "50", "correct_quantity": "beta", "restrict_angle": false, "right": "0.2", "close": "1.0", "C3": "25", "C1": "75"}, "variableReplacements": [], "scripts": {}}, {"variableReplacementStrategy": "originalfirst", "unitTests": [], "marks": "4", "customMarkingAlgorithm": "", "customName": "", "showCorrectAnswer": true, "extendBaseMarkingAlgorithm": true, "type": "angle-quantity-from-reference", "useCustomName": false, "showFeedbackIcon": true, "settings": {"C2": "50", "correct_quantity": "gamma", "restrict_angle": false, "right": "0.2", "close": "1.0", "C3": "25", "C1": "75"}, "variableReplacements": [], "scripts": {}}], "extendBaseMarkingAlgorithm": true, "type": "gapfill", "useCustomName": false, "showFeedbackIcon": true, "variableReplacements": [], "scripts": {}}, {"variableReplacementStrategy": "originalfirst", "unitTests": [], "marks": 0, "customMarkingAlgorithm": "", "customName": "", "prompt": "<p>Use the law of sines to determine the magnitudes of forces <strong>A</strong> and <strong>C</strong>.</p>\n<p><em>A</em> =&nbsp;[[0]]</p>\n<p><em>C</em> =&nbsp;[[1]]</p>\n<p></p>", "showCorrectAnswer": true, "sortAnswers": false, "gaps": [{"variableReplacementStrategy": "originalfirst", "unitTests": [], "marks": "4", "customMarkingAlgorithm": "", "customName": "", "showCorrectAnswer": true, "extendBaseMarkingAlgorithm": true, "type": "engineering-answer", "useCustomName": false, "showFeedbackIcon": true, "settings": {"C2": "50", "correctAnswer": "FA", "right": "0.2", "close": "1.0", "C3": "25", "C1": "75"}, "variableReplacements": [], "scripts": {}}, {"variableReplacementStrategy": "originalfirst", "unitTests": [], "marks": "4", "customMarkingAlgorithm": "", "customName": "", "showCorrectAnswer": true, "extendBaseMarkingAlgorithm": true, "type": "engineering-answer", "useCustomName": false, "showFeedbackIcon": true, "settings": {"C2": "50", "correctAnswer": "FC", "right": "0.2", "close": "1.0", "C3": "25", "C1": "75"}, "variableReplacements": [], "scripts": {}}], "extendBaseMarkingAlgorithm": true, "type": "gapfill", "useCustomName": false, "showFeedbackIcon": true, "variableReplacements": [], "scripts": {}}], "functions": {}, "preamble": {"css": "", "js": "Numbas.extensions.weh.scope.ggbApplet.then(function(applet){\n  applet.setValue('show',false);\n  applet.setValue('debug',false);\n});"}, "metadata": {"licence": "Creative Commons Attribution-NonCommercial 4.0 International", "description": "<p>Find the reactions of a rigid body (a triangular plate) at a pin and roller, using the three-force body principle.</p>"}, "type": "question", "variables": {"alpha1": {"group": "Inputs", "description": "", "definition": "random(25..60#5)", "name": "alpha1", "templateType": "anything"}, "theta": {"group": "Inputs", "description": "<p>reference direction. &nbsp;Set by student choice.</p>", "definition": "random(300..380#5)", "name": "theta", "templateType": "anything"}, "FB": {"group": "Inputs", "description": "", "definition": "qty(random(1..15)random(10,20,50),units[0])", "name": "FB", "templateType": "anything"}, "theta_a": {"group": "Ungrouped variables", "description": "", "definition": "qty(degrees(arctan(scalar(h/L))),'deg')", "name": "theta_a", "templateType": "anything"}, "beta": {"group": "Ungrouped variables", "description": "", "definition": "qty(90,'deg')- qty(degrees(arctan(scalar(h/l))),'deg')", "name": "beta", "templateType": "anything"}, "h": {"group": "Ungrouped variables", "description": "<p>this is the y-coordinate of the intersection point</p>", "definition": "l/2 ( (tan(radians(alpha1))) +  tan((radians(theta))))", "name": "h", "templateType": "anything"}, "FA": {"group": "Ungrouped variables", "description": "", "definition": "FB sin(scalar(alpha in 'radians'))/sin(scalar(beta in 'radians'))", "name": "FA", "templateType": "anything"}, "gamma": {"group": "Ungrouped variables", "description": "", "definition": "qty(180,'deg') - alpha -beta", "name": "gamma", "templateType": "anything"}, "debug": {"group": "Ungrouped variables", "description": "", "definition": "false", "name": "debug", "templateType": "anything"}, "units": {"group": "Inputs", "description": "", "definition": "random([['kN','m'],['lb','ft'], ['lb','in'],['N','m']])", "name": "units", "templateType": "anything"}, "alpha": {"group": "Ungrouped variables", "description": "", "definition": "qty(90-(360-theta),'deg')", "name": "alpha", "templateType": "anything"}, "L": {"group": "Inputs", "description": "", "definition": "qty(random(2..6#0.2),units[1])", "name": "L", "templateType": "anything"}, "FC": {"group": "Ungrouped variables", "description": "", "definition": "FB sin(scalar(gamma in 'radians'))/sin(scalar(beta in 'radians'))", "name": "FC", "templateType": "anything"}}, "advice": "<ol>\n<li>Draw a free body diagram.</li>\n<li>Apply $\\Sigma M_A$=0 to find the reaction at $C$. &nbsp;There's no x-component at $C$, because the support there is a roller. &nbsp;This should have been indicated on your free body diagram.</li>\n<li>Once $C$ and is&nbsp;known, apply $F_x = 0$ and $F_y=0$ to find components $A_x$ and $A_y$.</li>\n<li>With $A_x$ and $A_y$ known, use the pathagorean theorem to calculate the magnitude of $A$, and use trig to get the its direction.</li>\n</ol>", "extensions": ["geogebra", "quantities", "weh"], "name": "Equilibrium of a three-force body: triangle", "variablesTest": {"condition": "not (theta in [0,180,180+alpha1,360+alpha1,360-alpha1])", "maxRuns": 100}, "contributors": [{"name": "Xiaodan Leng", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/2146/"}, {"name": "William Haynes", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/2530/"}]}]}], "contributors": [{"name": "Xiaodan Leng", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/2146/"}, {"name": "William Haynes", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/2530/"}]}