- #1

whitejac

- 169

- 0

## Homework Statement

Determine the axial forces in the members of the truss and indicate whether they are in tension or compression.

## Homework Equations

Fx = 0

Fy = 0

Mp = 0

## The Attempt at a Solution

I attempted to find the reactions at the supports first. So:

Fx = 0 = Bx + 800cos(250)N

Fy = 0 = By + Cy + 800sin(250)N

Mb = 0 = Cy(1.4m) + 800cos(250)(0.4)Nm + 800sin(250)(0.7)Nm

These give

Cy = 454N

Bx = 273.6N

By = 297.8N

I found Alpha at A, that was 60.25, which gives an angle of 29.75 at the joint B.

(sorry the photo doesn't line up with the text, this was discovered after taking).

This would give Fy = Tab = 297.8/sin(29.75)

However, this is very much incorrect...

I'm legitimately lost and, if anyone helps me, please point out which assumptions i made incorrectly and at least a general idea of why they're incorrect. I won't respond well to vagueness because in my mind I've covered a lot of what I already know with some sense of logic as I've come to understand it.