Equilibrium of a rigid body: truss

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William Haynes

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William Haynes 1 year, 5 months ago

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Turned off debug mode (oops), and edited the ggb applet to turn off gridlines and scale.

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William Haynes 1 year, 11 months ago

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When b=2.8, h=4, B=2, C=5, F=4, E=3, then Ay = 0, but Numbas calculates it as Ay = -1.7763568394002505*10^(-15) and marks 0 wrong, because it calculates percent error to be 100 %

abs(0 - 0.00000000000002)/(0.00000000000002) = 1.

Added precround(Ay,6) in Marking settings to avoid this. I don't know how to fix the root cause.

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William Haynes 2 years, 10 months ago

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angle checker is broken, I'm turning it off for now

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Created this.

Name	Status	Author	Last Modified
Equilibrium of a rigid body: truss	Ready to use	William Haynes	05/10/2023 15:32
Equilibrium of a rigid body: triangle	Ready to use	William Haynes	01/04/2023 21:45
Three-force body method: triangle	Ready to use	William Haynes	12/02/2024 19:19
Equilibrium of a three-force body: triangle	draft	Xiaodan Leng	10/07/2019 21:37

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Question statement

{applet}

The truss shown consists of three sections {b} {units[1]} wide and {h} {units[1]} tall, subjected to the loads shown.

Determine the reactions at the pin and the roller.

D: {siground(D,3)} {units[0]}

A: {siground(magA,3)} {units[0]} at {siground(dirA,4)}° from the x-axis

Ax: {Ax} Ay: {Ay}

Give any introductory information the student needs.

			Name	Type	Generated Value

h	number	2.4
b	number	4
FB	integer	3
FC	integer	3
FF	integer	4
FE	integer	0
units	list	[ "kN", "m" ]

			Name	Type	Generated Value

params	dict	Dictionary with 10 entries
applet	ggbapplet	HTML node
debug	boolean	false

			Name	Type	Generated Value

D	number	2.5333333333
dirA	number	166.2637316944
Ay	number	1.4666666667
Ax	integer	-6
A	vector	vector(-6,1.4666666667)
magA	number	6.1766585717

Automatically regenerate variables?

Name

Data type

Value

xxxxxxxxxx
 
random(2..4#0.2)

JME function reference

Description

Describe what this variable represents, and list any assumptions made about its value.

Can an exam override the value of this variable?

Generated value: `number`

2.4

→ Used by:

D
params

This variable doesn't seem to be used anywhere.

Parts

Reactions at D Gap-fill
Reactions at A Gap-fill
Resultant at A Gap-fill
1. Gap angle Angle quantity 2020
  Add
2. Gap sign Choose one from a list
  Add
3. Gap ref Choose one from a list
  Add
4. Gap magA Engineering Accuracy with units
  Add

Gap-fill

Ask the student a question, and give any hints about how they should answer this part.

Use $\Sigma M_A = 0$ to find the vector components of $\textbf{D}$ .

$\textbf{D}_x =$ Dx Magnitude Dx Direction $\qquad \textbf{D}_y =$ Dy Magnitude Dy Direction

Advice

Draw a free body diagram.
Apply $\Sigma M_A$ = 0 to find the reaction at $D$. There's no x-component at $D$, because the support there is a roller. This should have been indicated on your free body diagram.
Once force $D$ and the loads are known, apply $\Sigma F_x = 0$ and $\Sigma F_y=0$ to find components $A_x$ and $A_y$.
With $A_x$ and $A_y$ known, use the pythagorean theorem to calculate the magnitude of force $A$, and use trig to get the its direction.

Give a worked solution to the whole question.

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Part	Test	Passed?
Gap-fill
Gap-fill		Hasn't run yet
Engineering Accuracy with units
Engineering Accuracy with units		Hasn't run yet
Choose one from a list
Choose one from a list		Hasn't run yet
Engineering Accuracy with units
Engineering Accuracy with units		Hasn't run yet
Choose one from a list
Choose one from a list		Hasn't run yet
Gap-fill
Gap-fill		Hasn't run yet
Engineering Accuracy with units
Engineering Accuracy with units		Hasn't run yet
Choose one from a list
Choose one from a list		Hasn't run yet
Engineering Accuracy with units
Engineering Accuracy with units		Hasn't run yet
Choose one from a list
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Gap-fill
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Angle quantity 2020
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Engineering Accuracy with units
Engineering Accuracy with units		Hasn't run yet

This question is used in the following exams:

test exam by Kathryn Jackson in Kathryn's workspace.
Chapter 5 Exercises by William Haynes in Engineering Statics.
Chapter 05 Exercises by Michael Proudman in Engineering Statics.
13. Equilibrium of Rigid Bodies by Michael Proudman in Engineering Statics.
studio 4 - Chapter 5 Exercises by Jay McCormack in studio 4.
studio 4 - Chapter 5 Exercises by Jay McCormack in Jay's workspace.
13. Equilibrium of Rigid Bodies by William Haynes in Engineering Statics.

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William Haynes 1 year, 5 months ago

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William Haynes 2 years, 10 months ago

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William Haynes 6 years, 7 months ago

William Haynes 6 years, 7 months ago

William Haynes 6 years, 7 months ago

Error in variable testing condition

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Warning

Generated value: `number`

Parts

Gap-fill

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Equilibrium of a rigid body: truss

Metadata

Taxonomy: mathcentre

Taxonomy: Kind of activity

Taxonomy: Context

Contributors

Feedback

History

Comment

Checkpoint description

William Haynes 1 year, 5 months ago

William Haynes 1 year, 11 months ago

William Haynes 2 years, 10 months ago

William Haynes 2 years, 10 months ago

William Haynes 3 years, 11 months ago

William Haynes 4 years, 2 months ago

William Haynes 4 years, 6 months ago

William Haynes 4 years, 11 months ago

William Haynes 4 years, 11 months ago

William Haynes 6 years, 6 months ago

William Haynes 6 years, 7 months ago

William Haynes 6 years, 7 months ago

William Haynes 6 years, 7 months ago

William Haynes 6 years, 7 months ago

Error in variable testing condition

Error

Warning

Generated value: number

Parts

Gap-fill

Generated value: `number`