# Vector Problem-Direction and Magnitude

1. Sep 9, 2007

### baseballer10p

1. The problem statement, all variables and given/known data
Determine the magnitude of the resultant force Fr=F1+F2 and its direction measured from the positive u axis.

2. Relevant equations
Law of Sines?

3. 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

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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Last edited: Sep 9, 2007
2. Sep 9, 2007

### rocomath

can't see your images, can you link it instead?

3. Sep 9, 2007

### baseballer10p

Yes, sir.

4. Sep 10, 2007

### learningphysics

The problem is that you're assuming F1 + F2 ends up along the u axis... it doesn't.

5. Sep 10, 2007

### baseballer10p

I have to use the angles to figure out which direction the resultant force is pointing after $$F_1$$ and $$F_2$$ are added, but I don't know how.

6. Sep 10, 2007

### learningphysics

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. Sep 18, 2007

### baseballer10p

Ok, thank you sir.

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