# Space turuss problem statics

1. Apr 21, 2012

### hurricane123

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

FIND A FORCE OF A 3-D TRUSS
2. Relevant equations
ƩFX=0
ƩFY=0
ƩFZ=0

3. The attempt at a solution
I figured out rB(2i,-1j,0), rc(2i,1j,0),rd(1i,0,2k) can you check if my vectors r right. After find the vectors of point B,C,D I calculated the unit vector, not I am stuck I dont what other information i need to find force at DG, need directions.
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

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2. Apr 23, 2012

### pongo38

You haven't declared your frame of reference, but it is implied by your equations, which are credible (rather than being 'right'). Your three relevant equations are for a two-dimensional situation. You can solve the problem by recognising that the applied forces and DG all lie in the xz plane, but if you are expected to solve the problem unnecessarily in three dimensions, how many relevant equations of equilibrium are there? Do you know how to express the moment of a force, using vector language?