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Homework Help: Force Vector into a Force (Power)

  1. Oct 14, 2008 #1
    1. The problem statement, all variables and given/known data

    Find the power input of a force vector F acting on a particle that moves with a velocity vector v for each of the following situations.
    (a) vector F = 4 N i hat + 3 N k hat , vector v = 9 m/s i hat

    2. Relevant equations

    P = F * V

    3. The attempt at a solution

    P =(4*9) +3

    Also tried

    P = SQRT(4^2+3^2) * 9
    I guess the problem is I don't know how to convert the vector 4i+3j into a force.
  2. jcsd
  3. Oct 14, 2008 #2


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    Homework Helper
    Gold Member

    That vector is the force. You have a force with an x component of 4N and a y component of 3N.

    In order to find the power you need to find the dot product of F and v:


    It seems like this was what you were trying to do in your first attempt. You made one small mistake. HINT: What is [itex]v_y[/itex]?
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