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Another Vector Question

  • Thread starter ThomasHW
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  • #1
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Homework Statement


http://www.tunerspec.ca/school/question7.jpg [Broken]

The Attempt at a Solution


Not sure where to start. I want to get the x & y coordinates of rAB but I'm not sure how.
 
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Answers and Replies

  • #2
learningphysics
Homework Helper
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Get the angle of vector OB from the positive x - axis going counterclockwise...
 
  • #3
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How? :uhh:
 
  • #5
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Using

[tex]tan x = \frac{711j}{418i}[/tex]

[tex]x = 59.55^{\circ}[/tex]
 
  • #6
learningphysics
Homework Helper
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Using

[tex]tan x = \frac{711j}{418i}[/tex]

[tex]x = 59.55^{\circ}[/tex]
good. what's the relationship between that OA and angle... and the OB angle?
 
  • #7
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I'm not sure...

If this ends up being easy I'm going to feel stupid. :tongue:
 
  • #8
Label the angle which is 59.55*. You have a triangle and 3 sides are known, use the cosine law to determine any angle right? From that you can get the angle that [tex]|r_{oa}+r_{ab}|[/tex] makes with the origin.

Then you can use the angle and sine/cosine to find the coords of the point B or you can set up a unit vector and multiply by the magnitude of the [tex]|r_{oa}+r_{ab}|[/tex] to get the components.
 
Last edited:
  • #9
learningphysics
Homework Helper
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I'm not sure...

If this ends up being easy I'm going to feel stupid. :tongue:
Oops... I thought I posted a reply. Sorry about that!

Use the angle AOB, and subtract it away from the angle of OA... that gives the angle of OB...
 
  • #10
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I'm getting a length of 824.77m for side OA. It looks too big according to the diagram, is it right?

Assuming it is...

I used the cosine law to determine the angle for AOB (43.99) and subtracted that from angle x (determined previously.) This gave me an angle of 15.56 from the x-axis to OB. Then using the length of 606m and the angle of 15.56 I determined the x and y coordinates to be 583.79m and 162.56m, respectively.

Is that right?
 
  • #11
learningphysics
Homework Helper
4,099
5
I'm getting a length of 824.77m for side OA. It looks too big according to the diagram, is it right?

Assuming it is...

I used the cosine law to determine the angle for AOB (43.99) and subtracted that from angle x (determined previously.) This gave me an angle of 15.56 from the x-axis to OB. Then using the length of 606m and the angle of 15.56 I determined the x and y coordinates to be 583.79m and 162.56m, respectively.

Is that right?
yup. looks right to me.
 
  • #12
53
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Thank you for the help. :)
 

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