// Numbas version: exam_results_page_options {"feedback": {"showanswerstate": true, "intro": "

Several exams in the past have started with a truss question followed by stresses in the truss members.

", "allowrevealanswer": true, "feedbackmessages": [], "advicethreshold": 0, "showtotalmark": true, "showactualmark": true}, "timing": {"timedwarning": {"action": "none", "message": ""}, "timeout": {"action": "none", "message": ""}, "allowPause": true}, "duration": 0, "percentPass": "50", "showstudentname": true, "name": "Basic Statics and Stresses in Trusses", "navigation": {"showfrontpage": true, "showresultspage": "oncompletion", "reverse": true, "browse": true, "onleave": {"action": "none", "message": ""}, "preventleave": true, "allowregen": true}, "showQuestionGroupNames": false, "metadata": {"licence": "Creative Commons Attribution 4.0 International", "description": "

Resolving forces in a simple truss, and 2D stresses in a uniaxially loaded bar.

"}, "question_groups": [{"name": "Truss", "pickingStrategy": "random-subset", "pickQuestions": 1, "questions": [{"name": "Triangular Truss", "extensions": [], "custom_part_types": [], "resources": [["question-resources/Truss-1.png", "/srv/numbas/media/question-resources/Truss-1.png"], ["question-resources/Truss-1_abNAGhD.png", "/srv/numbas/media/question-resources/Truss-1_abNAGhD.png"]], "navigation": {"allowregen": true, "showfrontpage": false, "preventleave": false, "typeendtoleave": false}, "contributors": [{"name": "Francis Franklin", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/1887/"}], "tags": [], "metadata": {"description": "

Tension in simple triangular truss.

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

Half of mechanics is about balancing forces. Some trusses can be treated like pin-jointed structures and decomposed into axial forces, i.e., without any bending or shear forces. The solution is therefore obtained through trigonometry.

", "advice": "

Balancing horizontal forces at B: $P_{AB}\\sin(\\var{theta})+P_{BC}\\sin(90-\\var{theta})=0$, or more simply: $P_{AB}\\sin(\\var{theta})+P_{BC}\\cos(\\var{theta})=0$.

Balancing vertical forces at B: $P_{AB}\\cos(\\var{theta})=P_{BC}\\cos(90-\\var{theta})+\\var{force}$, or more simply: $P_{AB}\\cos(\\var{theta})=P_{BC}\\sin(\\var{theta})+\\var{force}$,

where the units are kN. Multiplying the first by $\\cos(\\var{theta})$ and the second by $\\sin(\\var{theta})$, we get:

$P_{AB}\\sin(\\var{theta})\\cos(\\var{theta})+P_{BC}\\cos(\\var{theta})\\cos(\\var{theta})=0$

$P_{AB}\\cos(\\var{theta})\\sin(\\var{theta})-P_{BC}\\sin(\\var{theta})\\sin(\\var{theta})=\\var{force}\\sin(\\var{theta})$

and subtracting the second from the first:

$P_{BC}\\cos(\\var{theta})\\cos(\\var{theta})+P_{BC}\\sin(\\var{theta})\\sin(\\var{theta})=-\\var{force}\\sin(\\var{theta})$, or more simply: $P_{BC}=-\\var{force}\\sin(\\var{theta})$

since $\\cos^2 + \\sin^2 = 1$. Balancing vertical forces at C:

$P_{AC}+P_{BC}\\cos(90-\\var{theta})=0$, or more simply: $P_{AC}+P_{BC}\\sin(\\var{theta})=0$,

and substituting in the expression for $P_{BC}$ from above:

$P_{AC}-\\var{force}\\sin(\\var{theta})\\sin(\\var{theta})=0$,

the final answer simplifies to:

$P_{AC}=\\var{force}\\sin^2(\\var{theta})=\\var{siground(Pac,3)}$ [units: kN].

", "rulesets": {}, "builtin_constants": {"e": true, "pi,\u03c0": true, "i": true}, "constants": [], "variables": {"theta": {"name": "theta", "group": "Ungrouped variables", "definition": "random(35..55#5)", "description": "

Angle to vertical of Bar AB.

", "templateType": "anything", "can_override": false}, "Force": {"name": "Force", "group": "Ungrouped variables", "definition": "random(1..5)", "description": "

Applied vertical (downward) force.

", "templateType": "anything", "can_override": false}, "Pac": {"name": "Pac", "group": "Ungrouped variables", "definition": "force*(sin(radians(theta)))^2", "description": "

Tension in Bar AC.

", "templateType": "anything", "can_override": false}}, "variablesTest": {"condition": "", "maxRuns": 100}, "ungrouped_variables": ["Force", "theta", "Pac"], "variable_groups": [], "functions": {}, "preamble": {"js": "", "css": ""}, "parts": [{"type": "gapfill", "useCustomName": false, "customName": "", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "

A pin-jointed truss is shown in the figure below. The pivot at A is fixed, but the pivot at C is free to move vertically. The angle at B is a right angle.

$\"Pin-jointed$

If the applied force, $F$, is $\\var{force}$ kN vertically down, and the angle of Bar AB to the vertical, $\\theta$, is $\\var{theta}^\\circ$, what is the tension in Bar AC?

[[0]] [Units: kN]

", "gaps": [{"type": "numberentry", "useCustomName": false, "customName": "", "marks": "2", "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "Pac", "maxValue": "Pac", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "precisionType": "sigfig", "precision": "3", "precisionPartialCredit": "50", "precisionMessage": "You have not given your answer to the correct precision.", "strictPrecision": false, "showPrecisionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}], "sortAnswers": false}], "partsMode": "all", "maxMarks": 0, "objectives": [], "penalties": [], "objectiveVisibility": "always", "penaltyVisibility": "always"}, {"name": "Triangular Truss (On Floor)", "extensions": [], "custom_part_types": [], "resources": [["question-resources/Truss-1.png", "/srv/numbas/media/question-resources/Truss-1.png"], ["question-resources/Truss-1_abNAGhD.png", "/srv/numbas/media/question-resources/Truss-1_abNAGhD.png"], ["question-resources/Truss-2.png", "/srv/numbas/media/question-resources/Truss-2.png"]], "navigation": {"allowregen": true, "showfrontpage": false, "preventleave": false, "typeendtoleave": false}, "contributors": [{"name": "Francis Franklin", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/1887/"}], "tags": [], "metadata": {"description": "

Tension in a simple triangular truss.

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

", "advice": "

Balancing horizontal forces at B: $P_{AB}\\cos(\\var{theta})=P_{BC}\\sin(\\var{theta})$.

Balancing vertical forces at B: $P_{AB}\\sin(\\var{theta})+P_{BC}\\cos(\\var{theta})+\\var{force}=0$,

where units are kN. Multiplying the first by $\\sin(\\var{theta})$ and the second by $\\cos(\\var{theta})$ gives:

$P_{AB}\\sin(\\var{theta})\\cos(\\var{theta})-P_{BC}\\sin^2(\\var{theta})=0$

$P_{AB}\\sin(\\var{theta})\\cos(\\var{theta})+P_{BC}\\cos^2(\\var{theta})=-\\var{force}\\cos(\\var{theta})$

and subtracting the first from the second gives:

$P_{BC}\\sin^2(\\var{theta})+P_{BC}\\cos^2(\\var{theta})=-\\var{force}\\cos(\\var{theta})$,

or, since $\\sin^2+\\cos^2=1$:

$P_{BC}=-\\var{force}\\cos(\\var{theta})$.

Balancing horizontal forces at C: $P_{AC}+P_{BC}\\sin(\\var{theta})=0$

Substituting in the expression for $P_{BC}$ from above, and rearranging:

$P_{AC}=\\var{force}\\sin(\\var{theta})\\cos(\\var{theta}) = \\var{siground(Pac,3)}$ [units: kN].

Angle to vertical of Bar AB.

", "templateType": "anything", "can_override": false}, "Force": {"name": "Force", "group": "Ungrouped variables", "definition": "random(1..5)", "description": "

Applied vertical (downward) force.

", "templateType": "anything", "can_override": false}, "Pac": {"name": "Pac", "group": "Ungrouped variables", "definition": "force*sin(radians(theta))*cos(radians(theta))", "description": "

Tension in Bar AC.

A pin-jointed truss is shown in the figure below. The pivot at A is fixed, but the pivot at C is free to move horizontally. The angle at B is a right angle.

$\"Pin-jointed$

If the applied force, $F$, is $\\var{force}$ kN vertically down, and the angle of Bar AB to the horizontal, $\\theta$, is $\\var{theta}^\\circ$, what is the tension in Bar AC?

[[0]] [Units: kN]

", "gaps": [{"type": "numberentry", "useCustomName": false, "customName": "", "marks": "2", "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "Pac", "maxValue": "Pac", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "precisionType": "sigfig", "precision": "3", "precisionPartialCredit": "50", "precisionMessage": "You have not given your answer to the correct precision.", "strictPrecision": false, "showPrecisionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}], "sortAnswers": false}], "partsMode": "all", "maxMarks": 0, "objectives": [], "penalties": [], "objectiveVisibility": "always", "penaltyVisibility": "always"}, {"name": "Truss (Bracket)", "extensions": [], "custom_part_types": [], "resources": [["question-resources/Truss-1.png", "/srv/numbas/media/question-resources/Truss-1.png"], ["question-resources/Truss-1_abNAGhD.png", "/srv/numbas/media/question-resources/Truss-1_abNAGhD.png"], ["question-resources/Truss-3.png", "/srv/numbas/media/question-resources/Truss-3.png"]], "navigation": {"allowregen": true, "showfrontpage": false, "preventleave": false, "typeendtoleave": false}, "contributors": [{"name": "Francis Franklin", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/1887/"}], "tags": [], "metadata": {"description": "

Tension in bracket-truss.

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

", "advice": "

Balancing vertical forces at B: $P_{BC}\\sin(\\var{theta})+\\var{force}=0$,

where units are kN. Rearranging:

$P_{BC}=-\\var{force}/\\sin(\\var{theta}) = \\var{siground(Pbc,3)}$ [units: kN].

Angle to vertical of Bar AB.

", "templateType": "anything", "can_override": false}, "Force": {"name": "Force", "group": "Ungrouped variables", "definition": "random(1..5)", "description": "

Applied vertical (downward) force.

", "templateType": "anything", "can_override": false}, "Pbc": {"name": "Pbc", "group": "Ungrouped variables", "definition": "-force/sin(radians(theta))", "description": "

Tension in Bar BC.

", "templateType": "anything", "can_override": false}}, "variablesTest": {"condition": "", "maxRuns": 100}, "ungrouped_variables": ["Force", "theta", "Pbc"], "variable_groups": [], "functions": {}, "preamble": {"js": "", "css": ""}, "parts": [{"type": "gapfill", "useCustomName": false, "customName": "", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "

A pin-jointed truss is shown in the figure below. The pivots at A and C are fixed.

$\"Pin-jointed$

If the applied force, $F$, is $\\var{force}$ kN vertically down, and the angle between Bar AB and Bar BC, $\\theta$, is $\\var{theta}^\\circ$, what is the tension in Bar BC?

[[0]] [Units: kN]

", "gaps": [{"type": "numberentry", "useCustomName": false, "customName": "", "marks": "2", "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "Pbc", "maxValue": "Pbc", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "precisionType": "sigfig", "precision": "3", "precisionPartialCredit": "50", "precisionMessage": "You have not given your answer to the correct precision.", "strictPrecision": false, "showPrecisionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}], "sortAnswers": false}], "partsMode": "all", "maxMarks": 0, "objectives": [], "penalties": [], "objectiveVisibility": "always", "penaltyVisibility": "always"}]}, {"name": "Stress in Bar", "pickingStrategy": "all-ordered", "pickQuestions": 1, "questions": [{"name": "2D stress in a bar", "extensions": [], "custom_part_types": [], "resources": [["question-resources/Truss-4.png", "/srv/numbas/media/question-resources/Truss-4.png"]], "navigation": {"allowregen": true, "showfrontpage": false, "preventleave": false, "typeendtoleave": false}, "contributors": [{"name": "Francis Franklin", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/1887/"}], "tags": [], "metadata": {"description": "

Calculate direct and shear stress in an axially loaded bar in the XY plane.

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

Axial stress in a bar is a straightforward calculation, but $\\sigma_x$, $\\sigma_y$ and $\\tau_{xy}$ depend on the choice of $x$ and $y$ axes and the orientation of the bar.

", "advice": "

The bar has a solid square cross-section (10mm×10mm), so the cross-sectional area is 100mm$^2$.

The horizontal section area is 100mm$^2/\\sin(\\var{theta})=\\var{siground(AH,3)}$mm$^2$.
The vertical section area is 100mm$^2/\\cos(\\var{theta})=\\var{siground(AV,3)}$mm$^2$.
The axial stress is $\\var{force}$kN / 100mm$^2=\\var{SA}$MPa.
The direct stress in the $x$ direction is the force component in the $x$ direction ($F\\cos(\\theta)$) divided by the vertical section area, i.e.: $\\sigma_x= \\var{force}$kN $\\times \\cos^2(\\var{theta}) \\div 100$mm$^2 = \\var{siground(SX,3)}$MPa.
The direct stress in the $y$ direction is the force component in the $y$ direction ($F\\sin(\\theta)$) divided by the horizontal section area, i.e.: $\\sigma_y= \\var{force}$kN $\\times \\sin^2(\\var{theta}) \\div 100$mm$^2 = \\var{siground(SY,3)}$MPa.
The shear stress in the $xy$ plane is the force component in the $x$ direction ($F\\cos(\\theta)$) divided by the horizontal section area, or equivalently the force component in the $y$ direction ($F\\sin(\\theta)$) divided by the vertical section area, i.e.:? $\\tau_{xy}= \\var{force}$kN $\\times \\sin(\\var{theta})\\cos(\\var{theta}) \\div 100$mm$^2 = \\var{siground(TXY,3)}$MPa.

Angle of bar to x-axis.

", "templateType": "anything", "can_override": false}, "force": {"name": "force", "group": "Ungrouped variables", "definition": "random(-10..10 except 0)", "description": "

Applied axial load.

", "templateType": "anything", "can_override": false}, "AH": {"name": "AH", "group": "Ungrouped variables", "definition": "100/abs(sin(radians(theta)))", "description": "

Area of horizontal section.

", "templateType": "anything", "can_override": false}, "AV": {"name": "AV", "group": "Ungrouped variables", "definition": "100/abs(cos(radians(theta)))", "description": "

Area of vertical section

", "templateType": "anything", "can_override": false}, "SA": {"name": "SA", "group": "Ungrouped variables", "definition": "1000*force/100", "description": "

Axial stress.

", "templateType": "anything", "can_override": false}, "SX": {"name": "SX", "group": "Ungrouped variables", "definition": "1000*(force/100)*(cos(radians(theta)))^2", "description": "

Direct stress (sxx).

", "templateType": "anything", "can_override": false}, "SY": {"name": "SY", "group": "Ungrouped variables", "definition": "1000*(force/100)*(sin(radians(theta)))^2", "description": "

Direct stress (syy).

", "templateType": "anything", "can_override": false}, "TXY": {"name": "TXY", "group": "Ungrouped variables", "definition": "1000*(force/100)*sin(radians(theta))*cos(radians(theta))", "description": "

Shear stress (txy).

", "templateType": "anything", "can_override": false}}, "variablesTest": {"condition": "", "maxRuns": 100}, "ungrouped_variables": ["theta", "force", "AH", "AV", "SA", "SX", "SY", "TXY"], "variable_groups": [], "functions": {}, "preamble": {"js": "", "css": ""}, "parts": [{"type": "gapfill", "useCustomName": false, "customName": "", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "

The figure below shows a bar with axial load $F$, at angle $\\theta$ to the $x$ axis.

$\"Axially$

The bar has a solid square cross-section (10mm×10mm). If the axial load is $F=\\var{force}$ kN, and the angle is $\\theta=\\var{theta}^\\circ$:

What is the horizontal section area? [[0]] [Units: mm$^2$]
What is the vertical section area? [[1]] [Units: mm$^2$]
What is the axial stress? [[2]] [Units: MPa]
What is the direct stress in the $x$ direction? $\\sigma_x=$[[3]] [Units: MPa]
What is the direct stress in the $y$ direction? $\\sigma_y=$[[4]] [Units: MPa]
What is the shear stress in the $xy$ plane? $\\tau_{xy}=$[[5]] [Units: MPa]

", "gaps": [{"type": "numberentry", "useCustomName": true, "customName": "AH", "marks": "1", "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "AH", "maxValue": "AH", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "precisionType": "sigfig", "precision": "3", "precisionPartialCredit": "50", "precisionMessage": "You have not given your answer to the correct precision.", "strictPrecision": false, "showPrecisionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}, {"type": "numberentry", "useCustomName": true, "customName": "AV", "marks": "1", "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "AV", "maxValue": "AV", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "precisionType": "sigfig", "precision": "3", "precisionPartialCredit": "50", "precisionMessage": "You have not given your answer to the correct precision.", "strictPrecision": false, "showPrecisionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}, {"type": "numberentry", "useCustomName": true, "customName": "SA", "marks": "1", "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "SA", "maxValue": "SA", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "precisionType": "sigfig", "precision": "3", "precisionPartialCredit": "50", "precisionMessage": "You have not given your answer to the correct precision.", "strictPrecision": false, "showPrecisionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}, {"type": "numberentry", "useCustomName": true, "customName": "SX", "marks": "1", "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "SX", "maxValue": "SX", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "precisionType": "sigfig", "precision": "3", "precisionPartialCredit": "50", "precisionMessage": "You have not given your answer to the correct precision.", "strictPrecision": false, "showPrecisionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}, {"type": "numberentry", "useCustomName": true, "customName": "SY", "marks": "1", "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "SY", "maxValue": "SY", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "precisionType": "sigfig", "precision": "3", "precisionPartialCredit": "50", "precisionMessage": "You have not given your answer to the correct precision.", "strictPrecision": false, "showPrecisionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}, {"type": "numberentry", "useCustomName": true, "customName": "TXY", "marks": "1", "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "TXY", "maxValue": "TXY", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "precisionType": "sigfig", "precision": "3", "precisionPartialCredit": "50", "precisionMessage": "You have not given your answer to the correct precision.", "strictPrecision": false, "showPrecisionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}], "sortAnswers": false}], "partsMode": "all", "maxMarks": 0, "objectives": [], "penalties": [], "objectiveVisibility": "always", "penaltyVisibility": "always"}]}], "type": "exam", "contributors": [{"name": "Francis Franklin", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/1887/"}], "extensions": [], "custom_part_types": [], "resources": [["question-resources/Truss-1.png", "/srv/numbas/media/question-resources/Truss-1.png"], ["question-resources/Truss-1_abNAGhD.png", "/srv/numbas/media/question-resources/Truss-1_abNAGhD.png"], ["question-resources/Truss-2.png", "/srv/numbas/media/question-resources/Truss-2.png"], ["question-resources/Truss-3.png", "/srv/numbas/media/question-resources/Truss-3.png"], ["question-resources/Truss-4.png", "/srv/numbas/media/question-resources/Truss-4.png"]]}