Results 1 to 5 of 5

Math Help - Forces in Equilibrium (Vectors)

  1. #1
    Junior Member
    Joined
    Sep 2008
    Posts
    58

    Forces in Equilibrium (Vectors)

    Hey guys, I am stuck on this question. Can anyone give me some hints? I know the sum of the x and y components have to equal zero but I don't know how to find "the minimum". Here is the problem




    Thanks!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Senior Member bkarpuz's Avatar
    Joined
    Sep 2008
    From
    R
    Posts
    481
    Thanks
    2

    Exclamation

    Consider the following relations:
    F_{2}\sin(30)=F_{3}\sin(\alpha)
    and
    F_{2}\cos(30)+F_{3}\cos(\alpha)=F_{1}
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Sep 2008
    Posts
    58
    Yea I know how to get that far, but I don't know how to do the next parts. Finding F1 and alpha so F3 is a minimum.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor
    Joined
    Apr 2005
    Posts
    1,631
    Quote Originally Posted by Oblivionwarrior View Post
    Hey guys, I am stuck on this question. Can anyone give me some hints? I know the sum of the x and y components have to equal zero but I don't know how to find "the minimum". Here is the problem




    Thanks!
    Even just by looking at the diagram, the minimum F3 should be such thast F3 does not contribute to the F1. Meaning, F3 should have no horizontal component that would be pulled by F1.
    So minimum F3 has zero horizontal component,
    (F3)cos(alpha) = 0 -----(i)

    For Eq.(i) to be true, if F3 is not zero, the cos(alpha) should be zero, so,
    cos(alpha) = 0
    alpha = arccos(0) = 90 degrees, for minimum F3 ---------answer.
    And, minimum F3 = 137sin(30deg) = 68.5 newtons ------answer.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Junior Member
    Joined
    Sep 2008
    Posts
    58
    Thank you so much.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. polygon of forces to demonstrate equilibrium
    Posted in the Math Topics Forum
    Replies: 3
    Last Post: February 15th 2011, 02:48 PM
  2. equilibrium of forces
    Posted in the Math Topics Forum
    Replies: 9
    Last Post: December 30th 2008, 11:26 PM
  3. Equilibrium of forces... again
    Posted in the Math Topics Forum
    Replies: 9
    Last Post: December 30th 2008, 02:44 PM
  4. Forces in Equilibrium (Vectors) II
    Posted in the Advanced Applied Math Forum
    Replies: 14
    Last Post: October 2nd 2008, 06:43 PM
  5. Forces as a Vectors
    Posted in the Advanced Applied Math Forum
    Replies: 2
    Last Post: February 14th 2008, 04:17 PM

Search Tags


/mathhelpforum @mathhelpforum