DISCUSSION
Hints:
- In solving, it is suggested that you start out with the FBD of the pulley to find the reactions on the pulley at its center K. Note that you do NOT need to know the physical size of the pulley to find these reactions.
- After that, move through the solution using the equilibrium equations in the order of: Joint K, Joint H, Joint D, and Joint C.
Ask/answer questions in the discussion thread below.
is DK a zero force member? Are we to assume that the offset created by the pulley does not impact the direction of the force W applies on the truss? I guess in simpler terms, are we to assume W exerts a purely vertical force on the truss?
nevermind, I believe I have figured it out
I will follow up on this even if you have already figured it out.
Look at your FBD of the pulley. You will have a cable force acting to the right on the top of the pulley, and a cable force acting downward on the left side of the pulley. From this, you can readily find the reactions acting on the pulley by the truss through Newton’s 2nd law.
Next, look at the FBD of joint K of the truss. That FBD will have the reaction force on the truss due to the pulley, along with the loads carried by members (1) and (2).
From this, you can see that the actual size of the pulley does not influence the load on the truss. That may not have been obvious to you before you started looking at the FBDs.