(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Each of the three cables can safely carry a maximum tension force of 7.2kN. Based on this criterion, what is the largest safe mass of the suspended ceiling?

2. Relevant equations

Sum of forces=0

Sum of moments=0

3. The attempt at a solution

I drew this for the FBD:

I then tried to solve this by just summing all forces in the y-direction to get 'mg':

7.2kN*3-mg=0

m=2201.83kg, which isn't right.

So then I tried doing it by finding the moment about some arbitrary point (O):

[tex]\sum[/tex]M_{0}=-14*7.2i+5*7.2k+12*7.2k-7.2*7i-4Wk+8Wi=0

From which:

-14(7.2)-7.2(7)+8W=0 W=18.9kN

and from 5*7.2+12*7.2+4W=0 W=30.6

So those don't even give me the same value... What am I doing wrong? Wrong assumption about all tensions being 7.2kN?

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# Homework Help: 3D Force Equilibrium

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