How Are These Members in Compression and Tension

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SUMMARY

The discussion focuses on determining the forces in members of a truss system, specifically members CA and CB, under a 600N external force. The user initially concluded that member CB is in tension and member CA is in compression. However, the book states the opposite, indicating that member CA is in tension and member CB is in compression. The correct interpretation is that if member CB is applying force towards point C, it is indeed in compression, while member CA, acting downwards, is in tension.

PREREQUISITES
  • Understanding of static equilibrium equations
  • Knowledge of truss analysis and member forces
  • Familiarity with tension and compression concepts in structural engineering
  • Ability to interpret free body diagrams
NEXT STEPS
  • Study the principles of static equilibrium in truss systems
  • Learn how to analyze forces in truss members using methods such as the method of joints
  • Explore the differences between tension and compression in structural members
  • Review examples of free body diagrams in structural analysis
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Structural engineers, civil engineering students, and anyone involved in analyzing truss systems and understanding the behavior of structural members under load.

wahaj
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Homework Statement


I'm supposed to find the forces in each member and then determine whether they are in tension or compression. I got the magnitudes right but it seems my directions are wrong according to the book but I am confident that I did the question right. The diagram is part of a larger truss connected at point A and B so point A and B only have he forces shown in the free body diagram.

Homework Equations



statistical equilibrium equations

The Attempt at a Solution



Since the 600N external force is acting towards the right, then the horizontal component of force CB will act towards the left to balance everything out. This will result in the force CB facing towards point C. This means that member CB is in tension. Now since the vertical component of force CB is facing upwards force CA will act downwards to balance everything out which would result in member CA being in compression. But the book says that it is CA which is in tension and BC which is in compression. So who is right? Me or the book?
 

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wahaj said:
the horizontal component of force CB will act towards the left to balance everything out. This will result in the force CB facing towards point C. This means that member CB is in tension.
No, that's backwards. The force in question is the force the member CB is applying at point C. If that force is towards C then it means the member C is under compression.
As you know, action and reaction are equal and opposite. If the force from CB on the joint C is acting from B towards C then the force from the joint C on member CB is acting from C towards B.
 

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