Question

For the truss shown in the figure, the forces $F_1$ and $F_2$ are 9 kN and 3 kN, respectively. The force (in kN) in the member QS is (All dimensions are in m)

• A. 11.25 tension
• B. 11.25 compression
• C. 13.5 tension
• D. 13.5 compression

Answer 1

The correct option is C

13.5 tension

Section through PQ, QS, & ST (Figure - ii)
$\tan \theta =\frac{2}{1.5}={53.13}^{\circ }$

Considering L.H.S. of section (1)....(1)

$\sum F_v=0$

$-9+T_{SQ}\times \sin \theta =0$

$T_{SQ}=\frac{9}{\sin {53.13}^{\circ }}$

$=11.25kN\left(\text{Tensile}\right)$