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QLDEngineeringQuick questions
Unit 3: Civil structures
Quick questions on Forces, equilibrium and free-body diagrams for QCE Engineering Unit 3
4short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is force as a vector?Show answer
A force has magnitude (in newtons, ) and direction. Two forces can be added head-to-tail or, more usefully for calculation, split into perpendicular components. A force acting at angle to the horizontal has components:
What are free-body diagrams?Show answer
A free-body diagram isolates one body and shows every external force acting on it. Internal forces between parts of the same body are excluded. For a civil structure you typically draw:
What is the conditions of static equilibrium?Show answer
A rigid body is in static equilibrium when it has no tendency to translate or rotate. In two dimensions this gives three independent equations:
What are sign errors?Show answer
Pick one rotation direction as positive and keep it consistent. Mixing clockwise and anticlockwise positive within one equation is the most common arithmetic slip.
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