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Vector from origin problem

  1. Aug 31, 2008 #1
    i have no idea how to solve these 2 questions.. please direct me to the right way.

    1. Find the vector from the origin to the center of mass of a thin triangular plate (uniform density) whose vertices are A(7, 7, 2), B(7, 4, 6), and C(4, 10, 1).

    2. Find the area of the parallelogram determined by the points P(7, -5, 5), Q(4, 7, -3), R(-2,6,-4) and S(-5,18,-12)
    Last edited: Aug 31, 2008
  2. jcsd
  3. Aug 31, 2008 #2


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    First find the center of mass: hint in a triangle with uniform density, just average the coordinates of the vertices. (That doesn't work for a figure with more than three vertices.)

    Do you know the formula for area of a parallelogram? You can use that.

    Simpler is a formula from calculus: if [itex]\vec{u}[/itex] and [itex]\vec{v}[/itex] are vectors forming two adjacent sides of a parallelogram its area is [itex]|\vec{u}\times\vec{v}|[/itex].

    Now, do something yourself before expecting any further help!
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