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Draw the vectors head to tail so they make a triangle

  1. Feb 2, 2008 #1
    Draw the vectors head to tail so they make a triangle
     
    Last edited by a moderator: Jul 9, 2014
  2. jcsd
  3. Feb 2, 2008 #2

    Dick

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    Start with the first one. Draw the vectors head to tail so they make a triangle. The information they are giving you tells you some sides and angles in the triangle. Use trig.
     
  4. Feb 2, 2008 #3
    Ya thats the part I don't know how to do

    Because it # 11 it gives you Vector a = 5 cm long (the magnitude I believe) then it says C or the Resultant is also 5.0 cm long and the angle between A and C is 70 degrees I have no idea how to draw that. I'm used to going in the fashion of Vector A (polar or rectangular) + Vector B (polar or rectangular) + C (polar or rectangular) .. = Resultant

    or using the unit vector notation... And for these problems would I have to use the laws of sine and cosine or could I just do it with a vector additon method.
     
  5. Feb 2, 2008 #4

    Dick

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    Look at the second picture here. http://hyperphysics.phy-astr.gsu.edu/hbase/vect.html. Relabel R to C. That's the picture you should have. It's a triangle. Now fix the lengths and angles you match what you have. Looks to me like an isosceles triangle with side A=side C and an angle of 70 degrees between then. I would find the other angles just using that the sum of all of angle of a triangle is 180. Etc. Sure use things like the law of sines and law of cosines. You can't just directly use a vector addition method because you aren't given any components to add.
     
  6. Feb 2, 2008 #5
    Ya I always draw triangles just like that

    my problem is they only give the magnitude i believe for A and the magnitude for the resultant so how can I know in what direction the triangles should go ?
     
  7. Feb 2, 2008 #6

    Dick

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    You don't have to know that. They are only asking you for the magnitude of B and it's relative angles with the other vectors. You can't know anything about say, the orientation of the triangle. They don't give you enough information to determine that.
     
  8. Feb 2, 2008 #7
    So would I use the same method to solve the other #'s ? Thanks a million Dick.
     
  9. Feb 3, 2008 #8

    CompuChip

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    Where did the first post go? It just shows dots now... :confused:
     
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