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What is the scalar product V_1(DOT)V_2 ?

  1. Feb 28, 2010 #1
    1. The problem statement, all variables and given/known data

    Vector V_1 points along the z axis and has magnitude V_1 = 80. Vector V_2 lies in the xz plane, has magnitude V_2 = 51, and makes a -49o angle with the x axis (points below x axis)


    2. Relevant equations

    A.B=ABCos(theta)=AxBx+AyBy+AzBz

    Cos(theta)=(AxBx+AyBy+AzBz)/AB
    3. The attempt at a solution

    im not really sure where to go from here im not sure if those equations are useful
     
  2. jcsd
  3. Feb 28, 2010 #2

    kuruman

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    The equations are indeed useful. Find the x,y and z components of each vector, then apply the first equation that you posted.
     
  4. Feb 28, 2010 #3
    ok that helps a lot i dont know why i did do that. but how do you find the z component of the V_2=51?
     
    Last edited: Feb 28, 2010
  5. Feb 28, 2010 #4

    kuruman

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    Draw yourself two axes in the plane of the paper. Label the horizontal one x and the vertical one z (instead of the usual y). Draw the vector as indicated. Can you find its x and z components?
     
  6. Feb 28, 2010 #5
    ahh thanks that makes much more sense. i got the final answer to be -3079.2 which is indeed correct. the help is appreciated.
     
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