The force in the top member 6-7 needs to be determined when the 1,500
kg car is at joint 2.
First, solve for reactions R1 and R5 by applying
both the moment and force equilibrium equations for the whole truss.
-4 (14.72) + 16 R5 = 0
R5 = 3.68 kN
R1 + R5 - 14.72 =
R1 = 11.04 kN
Cut Truss at Required Member
Cut 1 Diagram
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.