Problem 342 | Equilibrium of Parallel Force System

The reaction at A is twice as the reaction at B
$R_A = 2R_B$
 

 

$\Sigma F_V = 0$

$R_A + R_B = 600 + 200$

$2R_B + R_B = 800$

$3R_B = 800$

$R_B = 266.67 \, \text{ lb}$
 

$\Sigma M_A = 0$

$600x + 200(x + 4) = 15R_B$

$600x + 200x + 800 = 15(266.67)$

$800x = 3200$

$x = 4 \, \text{ ft}$           answer