1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

What am I doing wrong on this Statics Problem?

  1. Jan 26, 2015 #1
    1. The problem statement, all variables and given/known data
    I signed up for Mechanics of Materials, but it turns out my statics is very rusty. Here is the problem, we are to compute the six component forces about the joints:

    twY08aU.png

    2. Relevant equations
    Force and moment equations are the name of the game.

    3. The attempt at a solution

    My problem arises thusly:

    I sum the moment about A. I place: C_x(.6)+(B_y).8=0. We know from the diagram that b_yu = 30. Simply solve this equation, and the result is C_x = 40. This is correct, according to the book.

    Now, I go to sum the moments about B, C_x(.6)+A_y(.8)=0. This yeilds A_y =30. According to the book A_u=0. What is invalid about my approach?

    Thanks a ton.
     
  2. jcsd
  3. Jan 26, 2015 #2
    Your equation assumes C_y is zero.

    Chet
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted