1. Not finding help here? Sign up for a free 30min 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!

Mechanics, Vector problem

  1. Sep 16, 2007 #1
    1. The problem statement, all variables and given/known data
    First of all I will have to apologize if this in in the wrong forum. It is a 1st year engineering mechanics problem.

    I am having an issue solving a secondary part of a question.
    The first part of the question has asked me to both graphically and numerically determine a resultant of three forces acting on an object, with magnitude and angles for all given. This was straightforward.
    I am now being asked to determine a fourth Force such that the resultant R of all the four forces will be vertical (90 degrees) and has a magnitude of 750 N.
    I have done this question graphically, but am wondering how I go about doing it numerically ..just buy using trig etc.
    thanks much,


    3. The attempt at a solution

    i have thus far determined that my previous resultant force was 821 N at 87 degrees North of East.
    I have therefore now said that my resultant is going to have to = 750 N so
    750 = (sum Fx + sum Fy)^(1/2).
    I am just unsure how I would go about getting two unkowns from this methodology, the X component and Y component of the unkown vector..
     
  2. jcsd
  3. Sep 16, 2007 #2

    learningphysics

    User Avatar
    Homework Helper

    What is the x - component of your 821N force ? Add to that and the x-component of your new force and you get 0. solve for the x-component of the new force.

    same way, solve for the y-component.
     
  4. Sep 16, 2007 #3
    Well the last resultant at a magnitude of 821N had 50.0007N (X-component) and 819.181N (Y component). Direction was 86.5 degrees N of E
    Now I need to add a Force such the new resultant will be 750N and vertical (or 90 degrees).
    I guess what I am saying is, I don't know how to get the X or Y component for my new force, becuase I don't know what it will be.
     
  5. Sep 16, 2007 #4

    learningphysics

    User Avatar
    Homework Helper

    50.0007N + Fx = 0, solve for Fx

    819.181N + Fy = 750, solve for Fy.
     
  6. Sep 16, 2007 #5
    of course.. how silly of me, I was trying to make a triangle and use law of cosines.. thanks much!
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Mechanics, Vector problem
Loading...