$\Sigma M_C = 0$
$5R_1 + 2(750) = 3000$
$R_1 = 300 \, \text{lb}$
$\Sigma M_A = 0$
$5R_2 + 3000 = 7(750)$
$R_2 = 450 \, \text{lb}$
To draw the Shear Diagram
- VA = R1 = 300 lb
- VB = VA + Area in load diagram
VB = 300 + 0 = 300 lb
- VC = VB + Area in load diagram
VC = 300 + 0 = 300 lb
VC2 = VC + R2 = 300 + 450 = 750 lb
- VD = VC2 + Area in load diagram
VD = 750 + 0 = 750
VD2 = VD - 750 = 750 - 750 = 0
To draw the Moment Diagram
- MA = 0
- MB = VA + Area in shear diagram
MB = 0 + 300(2) = 600 lb·ft
MB2 = VB - 3000
MB2 = 600 - 3000 = -2400 lb·ft
- MC = MB2 + Area in shear diagram
MC = -2400 + 300(3) = -1500 lb·ft
- MD = MC + Area in shear diagram
MD = -1500 + 750(2) = 0