# Problem 421 - Cantilever Truss by Method of Sections

**Problem 421**

Use the method of sections to compute for the force in members DF, EF, and EG of the cantilever truss described in Problem 411 and Fig. P-411.

**Solution 421**

$\Sigma M_E = 0$

$\frac{3}{\sqrt{13}}F_{DF}(\frac{40}{3}) = 100(20) + 200(10)$

$F_{DF} = 360.5551 ~ \text{kN}$ tension *answer*

$\Sigma M_A = 0$

$\frac{2}{\sqrt{5}}F_{EF}(20) = 200(20) + 200(10)$

$F_{EF} = 335.4102 ~ \text{kN}$ tension *answer*

$\Sigma M_F = 0$

$20F_{EG} = 100(30) + 200(20) + 200(10)$

$F_{EG} = 450 ~ \text{kN}$ compression *answer*

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