- #1

littlemac1

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Below is a sketch of a truss in which external support reactions are given as R1 = 0 kN, R2 = 3.5 kN, R3 = 4.5 kN. Members (M) are labeled in boxes, joints labeled in circles, and forces R.

Draw 2 Free body diagrams, one for each joints C and E.

Define what direction represents a positive force, and write equations for all forces acting on that joint.

View attachment 9138

For example, for joint D it's:

("SUM" is used for summation symbol)

SUMF

SUMF

SUMF

F4 = -9kN

View attachment 9139

Draw 2 Free body diagrams, one for each joints C and E.

Define what direction represents a positive force, and write equations for all forces acting on that joint.

View attachment 9138

For example, for joint D it's:

("SUM" is used for summation symbol)

SUMF

_{y}= 0SUMF

_{y}= F4 sin(30) + R3 = 0SUMF

_{y}= F4(1/2) + 4.5 kN = 0F4 = -9kN

View attachment 9139