# Help understanding how to determine Compress or Tension in Truss

1. Nov 28, 2013

### NoobeAtPhysics

1. The problem statement, all variables and given/known data

A small square truss shown is supported by a pin joint at I and a roller at A. Label all members of the
truss by Z (for zero force member), C (for compression) or T (for tension).

2. Relevant equations

3. The attempt at a solution

So this was an exam question on a past test and I have troubles understanding how to calculate this in a fast manner.

I usually just use method of joints for each member and determine it that way. But I don't know how to determine tension/compression by looking at a truss. I've asked a couple people but I never understand what they mean...

What is your guy's approach/thought process when solving this problem?

My next exam is coming soon and I really hope to get a better understanding of this!!

Thank you very much.

2. Nov 28, 2013

### SteamKing

Staff Emeritus
Start at the free end, point E, where the 100 N force is applied. What do you get for members DE and EF?

3. Nov 28, 2013

### NoobeAtPhysics

DE is compression and therfore EF is in tension

4. Nov 28, 2013

### SteamKing

Staff Emeritus
Good. Now work back towards the wall.