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!

Representing two couples by a force F

  1. May 1, 2014 #1
    1. The problem statement, all variables and given/known data

    Sorry if I posted in the wrong section, this is actually an App Maths question, but anyway

    The two shafts are subjected to the
    torques (couples) shown.

    (a) If you represent the two couples by a force F acting
    at the origin O and a couple M, what are F and M?

    (b) What is the magnitude of the total moment exerted
    by the two couples?

    Diagram:

    21ec0p3.jpg

    2. Relevant equations



    3. The attempt at a solution

    I do know what M is, long story but my final answer is 6.05Nm. I just don't get how to solve for F and I am completely stuck, any help ?
     
  2. jcsd
  3. May 1, 2014 #2
    ∑F=ma

    And check your units.
     
    Last edited: May 1, 2014
  4. May 2, 2014 #3

    BvU

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    I'm subscribing out of curiosity; could you fill in something under 2. and relate to us the long story ? I take it you added up the two pseudovectors ?
     
  5. May 2, 2014 #4
    Firstly I found the components of the moments by using simple trigonometry. I then summed them up and finally to get the magnitude I squared each component added them and took the square root
     
  6. May 2, 2014 #5

    SammyS

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    Do you have the dimensions of the cube ?
     

    Attached Files:

  7. May 2, 2014 #6
    Dimensions of the cube are irrelevant.
     
  8. May 3, 2014 #7
    No, the dimensions are not given. I think the force is zero because the two couples each have two equal and opposite forces(by definition of a couple) that would cancel. Is that correct ?
     
  9. May 3, 2014 #8

    SammyS

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    I think you are correct. ... but then I'm the guy who asked about dimensions.
     
  10. May 3, 2014 #9
    I agree the resultant force is zero.
     
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: Representing two couples by a force F
Loading...