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What is the scalar product V_1(DOT)V_2 ?

  • Thread starter Rellsun
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  • #1
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Homework Statement



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)


Homework Equations



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

Cos(theta)=(AxBx+AyBy+AzBz)/AB

The Attempt at a Solution



im not really sure where to go from here im not sure if those equations are useful
 

Answers and Replies

  • #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.
 
  • #3
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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?
 
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  • #4
kuruman
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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)
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?
 
  • #5
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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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