- #1
yaro99
- 75
- 0
Homework Statement
Homework Equations
∑Fx=0
∑Fy=0
∑M=0
The Attempt at a Solution
[/B]
I am just concerned with part a.
I got the correct answers doing this:
First, FBD of segment AB:
+cw ∑M_A=0: -136 - 6*By = 0
By = -22.7N
two ways to get Ay:
one:
+cw ∑M_B=0: -136 + 6*Ay = 0
Ay = 22.7N
two:
∑Fy=0: -22.7 + Ay = 0
Ay = 22.7N
FDB entire beam:
∑Fy=0: 22.7 - 22.7 + Cy = 0
Cy = 0
∑Fx=0: -440 + 220 + Cx = 0
Cx = 220N
Ok, so I got the correct answers. However, here is where I get confused. If I make a FBD on segment BC I get a different answer for Cy.
My attempt at a FBD:
this leads to either:
∑Fy=0: -22.7 + Cy = 0
Cy = 22.7N
or
+cw ∑M_B=0: -136 + 3*Cy = 0
Cy = 45.3N
Clearly my FBD is wrong for segment BC. I assume the correct FBD would have a zero reaction at point B; this would give the correct answer (0) for Cy. In order for Cy to be zero, there must be no forces or moment at point B in the FBD, but this doesn't make sense to me.