# Find Force exerted

(See attachments.)

FYI: In this posting I will write A (sub x) as Ax. I will Write Sigma (or sum) as {E}

Find the force exerted by pin A on the structure.

I know that I first make the free body diagram.

1. Try the entire frame: IN second attachment, image on left.

Problem...this is 4 unknowns, but we're only allowed 3 unknowns in a 2-D situation. The 4 are : Ax, Ay, Bx, By. The three eqns. available are {E}Fx=0 ; {E}Fy=0 ; {E}M=0

So, I decided that this won't work.

2. Try FBD of AD: the second attachment, image on right

Again there are 4 unknowns, this time they are Ax, Ay, Cx, Cy...This won't work.

However I think that I may be able to combine the two systems of equations.

-> Ax, Ay, Bx, By, Cx, Cy

Now what? I think I may have to solve for Ax and Ay? How do I finish this?

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#### Solution Preview

From 1st FBD, moment about B:

sum(M_B) = 0

=> Ay*5 - 80*(10+8) = 0

=> Ay = 80*18/5 = 288 lb (^: upward)

From second ...

#### Solution Summary

The solution provided help to find force exerted to complete the answer step-by-step equationally.