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!

Reaction Forces on members

  1. Oct 6, 2015 #1
    1. The problem statement, all variables and given/known data
    I am given the forces on picture and I´m asked to find the reactions on both supports. I see they are pin supports so they ask me for 4 unknowns.

    2. Relevant equations
    Sum of forces in both directions equal to zero
    Sum of torques wrt a convenient point equal to zero
    THREE equations in total, four unknowns.

    3. The attempt at a solution

    Sum of forces in both directions equal to zero
    Cx+Dx+200=0
    Cy+Dy-150=0
    Sum of torques wrt "C" equal to zero
    3(Dy)-1,5Dx-(3) 200+ (3)150=0

    Since I have THREE equations in total, four unknowns. I assumeI need to analyse members separately. I recall that members are supposed to be treated as weightless and subjected to two forces acting on the same line of action if they are part of a truss. However, Member ABC does´nt look like a truss member.

    If I analyse pin B I see it can only have horizontal forces acting on it pulling from both sides. Vertically it should have zero force. If I set Cy=0 it leads me to Dx and Dy not being zero both of them and I discovera contradictions if I analyse the member BD because it would have Dx and Dy novanishing and only a horizontal force on the x axis, which produces a pair acting on that member BD.
     

    Attached Files:

  2. jcsd
  3. Oct 6, 2015 #2

    SteamKing

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    You should analyze member ABC as a free body by itself, using the indicated applied forces. Because the entire mechanism is in static equilibrium, you will need some additional forces at pin B to keep ABC static. You can then analyze member BD by itself, since it must also be in static equilibrium, to find the reaction at D.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Reaction Forces on members
  1. Member force? (Replies: 3)

  2. Forces in members (Replies: 1)

Loading...