Finding shear force and bending moment in a beam

[Studious_stud]

Homework Statement

I am attempting to calculate the shear force Vx, and bending moment Mx within the interval C - D of this beam.

Homework Equations

ƩFy = 0
ƩMx = 0

The Attempt at a Solution

I have calculated the support reactions to be RA = 5kN and RB = 55kN

ƩFy = 0

5 + 55 - 10(x-4) - 10 - Vx = 0

ƩMx = 0

5x + 55(x-4) - 10(x-2) - 10((x-4)^2/2) - Mx = 0

I'm really not sure if this is correct or not! Any help would be greatly appreciated :)

Thanks all

 

[PhanthomJay]

These are not correct, it is easier to draw free body diagrams which cut through CD about the RIGHT end of the beam. The shear will jump right out at you. And for the moment in between C-D, use D as the origin of your x value, right to left for x.