Question

The axial forces in the members AB & BC of the cantilever truss as shown in figure are:

• A. $P,-P$
• B. $2.532P,-2.879P$
• C. $1.437P,2.569P$
• D. $1.547P,-1.243P$

Answer 1

The correct option is B $2.532P,-2.879P$

Let us consider equilibrium of joint 'B'


$\sum H=0$
$F_{AB}\cos {10}^o+F_{BC}\cos {30}^o=0...\left(1\right)$

$\sum V=0$
$F_{AB}\sin {10}^o+F_{BC}\sin {30}^o=-P...\left(2\right)$
From equation (1) & (2), we have
$F_{AB}=2.532P$

$F_{BC}=-2.879P$