Since, the member 6-7 needs to be determined, that member must be included
in the cut. However, there is is usually more than one location to make
It is easiest to make a cut where only three or less members are cut. Thus, a vertical cut through members 6-7, 6-3 and 2-3 was done as shown at the left. Notice that there are only three unknowns, which can be solved for with the three equilibrium equations.
ΣFy = 0
11.04 - 14.72 - F63 cos45 = 0
F63 = -5.204 kN
-4 (14.72) - 4cos45 F63 - 4sin45
F63 - 4 F67 = 0
-58.88 - 2 [(4) (0.7071) ( -5.204)] = 4 F67
F67 = -7.360 kN compression
For this cut location, you need to use at least two of the three equilibrium equations. The number of equations may be reduced by other cut locations.