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: Simple question about how to solve a force problem.

  1. Sep 8, 2010 #1
    I have to find the Force Horizontally and Vertically.

    My equation for Fh is cos(60)(AB) - cos(45)(BC) = 0
    My equation for Fv is sin 60 (AB) + sin 45 (BC) – 1000 = 0

    I dont recall how to move things around, what to divide etc. Basically i need a step by step explained so i can learn and recall hopefully how.

    These were rules for what to do also:

    You can use either equation to write an expression for either AB or BC, then substitute the value you find in the OTHER equation. You must substitute into the other equation in order to solve for an answer

    Please Help!
  2. jcsd
  3. Sep 8, 2010 #2


    User Avatar

    Staff: Mentor

    Welcome to the PF.

    What are AB and BC? Are they angles? I'd presume not, since you list other angles as arguments to the trig functions, but it's hard to be sure.

    Is there a diagram that goes with this problem that you can post? That would help a lot in giving you some hints on how to proceed.
  4. Sep 8, 2010 #3
    Here is the photo

    Attached Files:

  5. Sep 8, 2010 #4
    does that help at all?
  6. Sep 9, 2010 #5

    Doc Al

    User Avatar

    Staff: Mentor

    I assume that what you call AB is the reaction force RA and BC is the force RC.

    So you have two equations and two unknowns.

    This is a description of solving equations by substitution. Here's an example worked out: http://www.helpalgebra.com/onlinebook/substitutionmethod.htm" [Broken]

    Give it a try.
    Last edited by a moderator: May 4, 2017
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook