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!

Homework Help: How do I know which direction the horizontal force acts

  1. Apr 30, 2015 #1
    1. The problem statement, all variables and given/known data
    I am to find the reactions of a 3 pin frame.

    2. Relevant equations

    3. The attempt at a solution
    So how do I know which direction to label the horizontal reactions? In the diagram HA and HF are in the same direction, I was under the impression that reactions are opposite to applied force. Photo 30-04-2015 21 44 56.jpg

    I have no problems calculating a solution once i know which direction the reaction occurs.
  2. jcsd
  3. Apr 30, 2015 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    Uhh, looks like someone has drawn in the direction of the horizontal forces at pins A and F.

    This is why PF Rules request that posters provide a complete description of the HW problem and use of the HW template.
  4. Apr 30, 2015 #3
    Yes that was me. I know the method to calculate a solution providing I know which directions the horizontal reaction forces act.

    My question was how do I know which direction the reaction forces act or what bit of information in that diagram tells me that HA and HF both act to the Right.
  5. May 1, 2015 #4


    User Avatar
    Gold Member

    If you draw the forces in the wrong direction, you will simply get a negative number in your answer!
  6. May 1, 2015 #5
    I have already solved my problem and would have marked it solved if i knew how. Your answer was the one I was looking for, thank you for taking the time to read the problem and reply.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted