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Vector Problem-Direction and Magnitude

  • #1

Homework Statement


Determine the magnitude of the resultant force Fr=F1+F2 and its direction measured from the positive u axis.
staticsproblem.jpg



Homework Equations


Law of Sines?


The Attempt at a Solution


I drew parallel lines and attempted to use the sine law, but I got two different answers.
Here's the equations I used:
Fr/sin100 = 200/sin50
Fr/sin100 = 300/sin30


staticsproblem2.jpg


Using these equations, I got two different answers for Fr, and didn't get any direction.


Other than what I tried, I don't know what to do. We weren't taught how to find the magnitude from components or taught how to find direction.
 

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Answers and Replies

  • #2
1,752
1
can't see your images, can you link it instead?
 
  • #4
learningphysics
Homework Helper
4,099
5
The problem is that you're assuming F1 + F2 ends up along the u axis... it doesn't.
 
  • #5
I have to use the angles to figure out which direction the resultant force is pointing after [tex]F_1[/tex] and [tex]F_2[/tex] are added, but I don't know how.
 
  • #6
learningphysics
Homework Helper
4,099
5
The things you know for sure are the 200, 300 sides... and the 100 degrees angle. You can use those to get the magnitude of F1+F2, and the angles....

Draw a triangle separately from the axes... when you get the angles... then you can draw F1+F2 in correctly...
 
  • #7
Ok, thank you sir.
 

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