- #1

neeboy74

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## Homework Statement

"A lifting mechanism is mounted on the back of a truck as shown: Calculate the forces in each member and the reactions @ A & B for alpha=0

## Homework Equations

Sum of moments about A=0:

0=(5000N)(1m)+(-5000N)(-1.25m)+(By)(.5m)

By=2500N

## The Attempt at a Solution

I treated the entire assembly as a rigid body to get the force By above; that would make Ay=2500N, correct?

I have drawn the entire FDB in AutoCAD, and have found the following:

BD=6250N

CD=3750N

AB=2500N

AC=5590.167N

BC=5000N

I have attached a scan of the problem. Now, having said all of that, is my general thinking ok? We're supposed to be able to figure out the reactions @ A and B using the method of joints, but I'm having real trouble with that. I found the reactions by using moments around A and then summing my forces in the Y direction=0, and got my forces in the members by using trig, but I also need to figure out which members are in tension/compression, again, using method of joints. If someone could step me through finding the forces at any two joints, I think that in itself would be a very helpful start! Thanks in advance for any/all helpful replies