// Numbas version: exam_results_page_options
{"name": "12. Free Body Diagrams", "metadata": {"description": "<p>Homework set. &nbsp;Identify student errors when drawing free body diagrams.</p>", "licence": "Creative Commons Attribution-ShareAlike 4.0 International"}, "duration": 0, "percentPass": 0, "showQuestionGroupNames": false, "shuffleQuestionGroups": false, "showstudentname": true, "question_groups": [{"name": "Group", "pickingStrategy": "all-ordered", "pickQuestions": 1, "questionNames": ["", ""], "variable_overrides": [[], []], "questions": [{"name": "Free Body Diagram 1", "extensions": [], "custom_part_types": [], "resources": [["question-resources/fbd-0_PoiZpWl.png", "/srv/numbas/media/question-resources/fbd-0_PoiZpWl.png"], ["question-resources/fbd-1_xI6ep5I.png", "/srv/numbas/media/question-resources/fbd-1_xI6ep5I.png"], ["question-resources/fbd-2_AdzNdwg.png", "/srv/numbas/media/question-resources/fbd-2_AdzNdwg.png"], ["question-resources/fbd-4_kKlRsW2.png", "/srv/numbas/media/question-resources/fbd-4_kKlRsW2.png"], ["question-resources/fbd-5_zSYquRr.png", "/srv/numbas/media/question-resources/fbd-5_zSYquRr.png"], ["question-resources/fbd-3_frDmR9m.png", "/srv/numbas/media/question-resources/fbd-3_frDmR9m.png"]], "navigation": {"allowregen": true, "showfrontpage": false, "preventleave": false, "typeendtoleave": false}, "contributors": [{"name": "William Haynes", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/2530/"}], "tags": [], "metadata": {"description": "Identify errors in student-drawn free body diagrams of a rigid body.", "licence": "Creative Commons Attribution-NonCommercial 4.0 International"}, "statement": "<p>Identify the errors (if any) in the&nbsp;student's free body diagram of the smooth bar $ACB$, pinned at $A$.</p>\n<div>\n<table width=\"767\" height=\"317\" align=\"left\">\n<tbody>\n<tr>\n<td style=\"width: 396.1875px; text-align: left;\"><img src=\"resources/question-resources/fbd-0_PoiZpWl.png\"/></td>\n<td style=\"width: 337.828125px;\">\n<p style=\"text-align: left;\">{image('resources/question-resources/'+this['filename'])}</p>\n</td>\n</tr>\n</tbody>\n</table>\n</div>\n<p></p>", "advice": "<p>{mistakes}&nbsp;</p>\n<ol>\n<li>When isolating the body, don't draw the pin at $C$.</li>\n<li>The pin connection at $A$ should be represented by $A_x$ and $A_y$.</li>\n<li>The force at $C$ has a known direction, perpendicular to bar $ACB$. &nbsp;It is best to draw it at that angle rather than breaking it into components</li>\n</ol>", "rulesets": {}, "builtin_constants": {"e": true, "pi,\u03c0": true, "i": true}, "constants": [], "variables": {"mistakes": {"name": "mistakes", "group": "Ungrouped variables", "definition": "this['errors']", "description": "<p>the student's mistakes to be found</p>", "templateType": "anything", "can_override": false}, "choices": {"name": "choices", "group": "Ungrouped variables", "definition": "[\n\"Body incorrectly isolated from supports\",\n\"Missing labels\",\n\"Incorrect labeling\",\n\"Missing arrowheads\",\n\"Incorrect represention at A\",\n\"Incorrect represention at B\",\n\"Incorrect represention at C\",\n\"Extra forces\",\n\"Missing weight\",\n\"Force with known direction shown as components\",\n\"No errors\"\n]\n\n", "description": "<p>list of possible mistakes -- checkbox labels</p>", "templateType": "anything", "can_override": false}, "fbds": {"name": "fbds", "group": "Ungrouped variables", "definition": "json_decode(safe(\"[\\n    {\\n        \\\"filename\\\": \\\"fbd-1_xI6ep5I.png\\\",\\n        \\\"errors\\\": [\\n            \\\"Body incorrectly isolated from supports\\\",\\n            \\\"Incorrect represention at C\\\"\\n        ]\\n    },\\n    {\\n        \\\"filename\\\": \\\"fbd-2_AdzNdwg.png\\\",\\n        \\\"errors\\\": [\\n            \\\"Body incorrectly isolated from supports\\\"\\n        ]\\n    },\\n    {\\n        \\\"filename\\\": \\\"fbd-3_frDmR9m.png\\\",\\n        \\\"errors\\\": [\\n            \\\"Body incorrectly isolated from supports\\\",\\n            \\\"Incorrect labeling\\\",\\n            \\\"Missing labels\\\",\\n            \\\"Missing arrowheads\\\",\\n            \\\"Incorrect represention at A\\\",\\n            \\\"Incorrect represention at C\\\"\\n        ]\\n    },\\n    {\\n        \\\"filename\\\": \\\"fbd-4_kKlRsW2.png\\\",\\n        \\\"errors\\\": [\\n            \\\"Incorrect represention at C\\\"\\n        ]\\n    },\\n    {\\n        \\\"filename\\\": \\\"fbd-5_zSYquRr.png\\\",\\n        \\\"errors\\\": [\\n            \\\"Incorrect represention at C\\\",\\n            \\\"Force with known direction shown as components\\\"\\n        ]\\n    }\\n]\"))", "description": "<p>array containing problem image file name and cooresponding errors</p>", "templateType": "json", "can_override": false}, "this": {"name": "this", "group": "Ungrouped variables", "definition": "fbds[index]", "description": "<p>the current fbd and mistakes</p>", "templateType": "anything", "can_override": false}, "index": {"name": "index", "group": "Ungrouped variables", "definition": "random(0..length(fbds)-1)", "description": "<p>Selects the FBD to show.</p>\n<p></p>\n<p></p>", "templateType": "anything", "can_override": false}, "matrix": {"name": "matrix", "group": "Ungrouped variables", "definition": "map(if(indices(mistakes, d)=[],0,1),d,choices)", "description": "<p>the marking matrix. &nbsp;0 if item should not be selected, 1 if it should</p>", "templateType": "anything", "can_override": true}}, "variablesTest": {"condition": "", "maxRuns": 100}, "ungrouped_variables": ["fbds", "this", "mistakes", "choices", "index", "matrix"], "variable_groups": [], "functions": {}, "preamble": {"js": "", "css": "img{width:600px;}"}, "parts": [{"type": "m_n_2", "useCustomName": false, "customName": "", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": false, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "<p><strong>Check {length(mistakes)} </strong><strong>{pluralise(length(mistakes),\"box\",\"boxes\")}.</strong></p>", "minMarks": "0", "maxMarks": "10", "shuffleChoices": false, "displayType": "checkbox", "displayColumns": "2", "minAnswers": "length(mistakes)", "maxAnswers": "length(mistakes)", "warningType": "none", "showCellAnswerState": true, "markingMethod": "all-or-nothing", "choices": "choices", "matrix": "matrix"}], "partsMode": "all", "maxMarks": 0, "objectives": [], "penalties": [], "objectiveVisibility": "always", "penaltyVisibility": "always"}, {"name": "Free Body Diagram 2", "extensions": [], "custom_part_types": [], "resources": [["question-resources/fbd-0_mCuZXP7.png", "/srv/numbas/media/question-resources/fbd-0_mCuZXP7.png"], ["question-resources/fbd-1_A1jE3RW.png", "/srv/numbas/media/question-resources/fbd-1_A1jE3RW.png"], ["question-resources/fbd-2_AsVnLti.png", "/srv/numbas/media/question-resources/fbd-2_AsVnLti.png"], ["question-resources/fbd-3_R8yRyT1.png", "/srv/numbas/media/question-resources/fbd-3_R8yRyT1.png"], ["question-resources/fbd-4_t09hKMf.png", "/srv/numbas/media/question-resources/fbd-4_t09hKMf.png"], ["question-resources/fbd-5_R9qCm5N.png", "/srv/numbas/media/question-resources/fbd-5_R9qCm5N.png"]], "navigation": {"allowregen": true, "showfrontpage": false, "preventleave": false, "typeendtoleave": false}, "contributors": [{"name": "William Haynes", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/2530/"}], "tags": [], "metadata": {"description": "Identify errors in student-drawn free body diagrams of a rigid body.", "licence": "Creative Commons Attribution-NonCommercial 4.0 International"}, "statement": "<p>Identify the errors (if any) in the&nbsp;student's free body diagram of post&nbsp;$CD$. &nbsp;Contact at $C$ is frictionless. &nbsp;Both pieces have non-negligible weight.</p>\n<div>\n<table width=\"767\" height=\"317\" align=\"left\">\n<tbody>\n<tr>\n<td style=\"width: 396.1875px; text-align: left;\"><img src=\"resources/question-resources/fbd-0_mCuZXP7.png\"/></td>\n<td style=\"width: 337.828125px;\">\n<p style=\"text-align: left;\">{image('resources/question-resources/'+this['filename'])}</p>\n</td>\n</tr>\n</tbody>\n</table>\n</div>\n<p></p>", "advice": "<p>{mistakes}&nbsp;</p>\n<ol>\n<li>Because the contact at $C$ is frictionless the force acts perpendicular to bar $ACB$ and should be drawn acting in that direction, although it is not strictly an error to dry components $C_x$ and $C_y$ this tends to lead to errors.</li>\n<li>You can't push a rope, so the force of the cable on the post acts to the left.</li>\n<li>There is a fixed connection at $D$, so that should be represented by $D_x, D_y$ and a moment.</li>\n<li>Since there is a non-negliable weight, don't forget the weight vector pointing down at the center of gravity.</li>\n</ol>", "rulesets": {}, "builtin_constants": {"e": true, "pi,\u03c0": true, "i": true}, "constants": [], "variables": {"mistakes": {"name": "mistakes", "group": "Ungrouped variables", "definition": "this['errors']", "description": "<p>the mistakes to be identified</p>", "templateType": "anything", "can_override": false}, "choices": {"name": "choices", "group": "Ungrouped variables", "definition": "[\n\"Body incorrectly isolated from supports\",\n\"Missing labels\",\n\"Incorrect labeling\",\n\"Missing arrowheads\",\n\"Tension wrong direction\",\n\"Incorrect reaction at C\",\n\"Incorrect reaction at D\",\n\"Extra forces\",\n\"Missing weight\",\n\"Force with known direction shown as components\",\n\"No errors\"\n]\n\n", "description": "<p>list of possible mistakes -- checkbox labels</p>", "templateType": "anything", "can_override": false}, "fbds": {"name": "fbds", "group": "Ungrouped variables", "definition": "json_decode(safe(\"[\\n    {\\n        \\\"filename\\\": \\\"fbd-1_A1jE3RW.png\\\",\\n        \\\"errors\\\": [\\n            \\\"No errors\\\"\\n        ]\\n    },\\n    {\\n        \\\"filename\\\": \\\"fbd-2_AsVnLti.png\\\",\\n        \\\"errors\\\": [\\n            \\\"Incorrect reaction at D\\\",\\n            \\\"Missing weight\\\"\\n        ]\\n    },\\n    {\\n        \\\"filename\\\": \\\"fbd-3_R8yRyT1.png\\\",\\n        \\\"errors\\\": [\\n            \\\"Tension wrong direction\\\",\\n            \\\"Incorrect reaction at C\\\",\\n            \\\"Missing weight\\\"\\n        ]\\n    },\\n    {\\n        \\\"filename\\\": \\\"fbd-4_t09hKMf.png\\\",\\n        \\\"errors\\\": [\\n            \\\"Tension wrong direction\\\",\\n            \\\"Incorrect labeling\\\",\\n            \\\"Incorrect reaction at D\\\",\\n            \\\"Missing weight\\\",\\n            \\\"Force with known direction shown as components\\\"\\n        ]\\n    },\\n    {\\n        \\\"filename\\\": \\\"fbd-5_R9qCm5N.png\\\",\\n        \\\"errors\\\": [\\n            \\\"Missing labels\\\",\\n            \\\"Incorrect labeling\\\",\\n            \\\"Incorrect reaction at C\\\",\\n            \\\"Incorrect reaction at D\\\",\\n            \\\"Missing weight\\\"\\n        ]\\n    }\\n]\"))", "description": "<p>array containing problem image file name and cooresponding errors</p>", "templateType": "json", "can_override": false}, "this": {"name": "this", "group": "Ungrouped variables", "definition": "fbds[index]", "description": "<p>the current fbd and mistakes</p>", "templateType": "anything", "can_override": false}, "index": {"name": "index", "group": "Ungrouped variables", "definition": "random(0..length(fbds)-1)", "description": "<p>selects the fbd for the question</p>\n<p></p>\n<p></p>", "templateType": "anything", "can_override": false}, "matrix": {"name": "matrix", "group": "Ungrouped variables", "definition": "map(if(indices(mistakes, d)=[],0,1),d,choices)", "description": "<p>the marking matrix. &nbsp;For each checkbox, 0 if not a mistake, 1 if a mistake.</p>", "templateType": "anything", "can_override": false}}, "variablesTest": {"condition": "", "maxRuns": 100}, "ungrouped_variables": ["fbds", "this", "mistakes", "choices", "index", "matrix"], "variable_groups": [], "functions": {}, "preamble": {"js": "", "css": "img{width:600px;}"}, "parts": [{"type": "m_n_2", "useCustomName": false, "customName": "", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "mark:\n  assert(marks>0,correct());  // any answer is correct when 0 marks are available\n  assert(numTicks>0,\n    warn(translate(\"part.marking.nothing entered\"));\n    fail(translate(\"part.marking.nothing entered\"))\n  );\n  apply(same_ticks)\n\nshould_be_ticked (A chocie should be ticked if it's awarded ap ositive number of marks):\n  map(map(y>0,y,row),row,settings[\"matrix\"])\n\nsame_ticks (Did the student tick the same choices as the expected answer?):\n  correctif(studentanswer=should_be_ticked)\n\n", 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