Results 1 to 1 of 1

Math Help - Vectors, Forces and Moments

  1. #1
    Junior Member
    Joined
    May 2010
    Posts
    36

    Vectors, Forces and Moments

    In a past paper I came across this question which I tried very hard to solve with no luck:

    The moment vector M of a vector B about the point A is found by the formula:

    M = r x B

    where r is the vector from point A to the position where vector B is applied.

    A force F = 3i - 4j + k Newtons act at P, having co-cordinates (-2,3,5) meters.

    a) Find the moment vector of force F about point A, having co-ordinates (0,-1,-3), and hence find the magnitude of this moment.

    r = -2i + 4j - 8k
    |M| = 44.45Nm


    b) Find two possible points R1 and R2, both having equal y and z co-ordinates, around which the magnitude of the moment of the same force F is maximum and that are at a distance 5\sqrt{3} meters from point P.

    I deduced that the line passing through R1 and R2 has perpendicular to the force (for it to be max). I tried to prove with dot product of line (R1R2) with the Force F. Would it be a good idea to try working with point P on the same line of R1 and R2 as long as they are at the mentioned distance from point P. attached.
    Attached Thumbnails Attached Thumbnails Vectors, Forces and Moments-photo.jpg  
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. moments-with forces applied at an angle.
    Posted in the Trigonometry Forum
    Replies: 2
    Last Post: December 9th 2008, 09:52 AM
  2. Forces in Equilibrium (Vectors) II
    Posted in the Advanced Applied Math Forum
    Replies: 14
    Last Post: October 2nd 2008, 06:43 PM
  3. Forces in Equilibrium (Vectors)
    Posted in the Advanced Applied Math Forum
    Replies: 4
    Last Post: September 27th 2008, 08:57 PM
  4. Forces and Vectors
    Posted in the Trigonometry Forum
    Replies: 4
    Last Post: August 18th 2008, 04:43 AM
  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