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Homework Help: Vector component question

  1. Jan 26, 2012 #1
    This question was just given on a CEE 270 exam (handwritten by professor). The way it's written doesn't make any sense to me.

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

    A force vector
    [itex]\vec{F}[/itex] = ([itex]70.0 \hat{i} + F_{y} \hat{j} + 140.0 \hat{k}[/itex] ) N​

    has a component of +20.0 N in the direction defined by the vector
    [itex]\vec{P}[/itex] = ([itex]6 \hat{i} - 3 \hat{j} - 2 \hat{k}[/itex] ) kN​

    Solve for [itex]F_{y}[/itex].

    3. The attempt at a solution

    I asked the professor if I needed to rotate the coordinate system as the question states that a component of [itex]\vec{F}[/itex] is in the [itex]\vec{P}[/itex] direction. He said no rotation of the coordinate system should be needed.

    I am very confused at how to even approach this problem. Please help. Does it even make sense?
  2. jcsd
  3. Jan 26, 2012 #2


    User Avatar

    Staff: Mentor

    The problem makes sense. When you want to know the projection of one vector onto another, what vector operation comes to mind?
  4. Jan 26, 2012 #3
    Wow... I didn't recognize it as a vector projection problem.... Thank you!
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