Finding the unknown forces at two supporting pins

[ptguard1]

Homework Statement

In a simple truss where P = 8 kip, find the unknown forces D_x, D_y, C_x, and C_y then determine the average normal stress in each member.

Description of truss:

I cannot copy an image due to the source it is coming from, so here is my attempt at a description

A triangle with arms AB (going up and to the right (5 feet)), BD (going down and to the right(5 feet)), and DA (going to the left connecting back with A (8 feet)). Member BE cutting straight down the middle of the triangle (3 feet). Member BC parallel with member ED and equal length of 4 feet. Pins at C and D. The force P is applied downward at point A and the force 0.75P is applied downward at point E.

Homework Equations

The Attempt at a Solution

I know that in a 2D problem you can only have three unknowns to find the forces. I am able to find C_x and D_x to be 29.3 kip (D_x in the negative x direction), but cannot remember how to find the y values.

 

[grzz]

I am having difficulty downloading the attachament.

 

[ptguard1]

I went ahead and made a rough sketch on paint

 

[nvn]

ptguard1: The force in truss members is always axial. Therefore, you know C_y = 0.

 

[ptguard1]

What do you mean by an axial force?

 

[nvn]

ptguard1: The direction of the resultant (i.e., total) force in each truss member is always along the longitudinal centerline of each truss member. A force along the longitudinal centerline of a member is called an axial force.

 

[ptguard1]

I just discovered that I actually didn't need to find the forces at each pin in order to solve the overall problem, but thank you for the information.