Determining Force of Fb: Homework Statement

[Eternal Sky]

Homework Statement

Two forces, Fa and Fb, act on an object located at the origin. Fa has a force of 4500 N and has an angle of 60 degrees with respect to the positive x-axis. Fb has an angle of 140 degrees with respect to the positive x-axis. Determine the force of Fb.

Homework Equations

Component vector equations (possibly):

sin θ = Vy/V

cos θ = Vx/V

tan θ = Vy/Vx

V^2 = Vx^2 + Vy^2

Newton's Second Law:

F = ma

The Attempt at a Solution

I split up Fa into it's components, but that didn't really help me to solve for Fb. I also had the idea of using the law of sines:

sin 140/4500 N = sin 60/b

However, the answer came out to 6062 N, and my textbook has the answer listed as 6890 N. Besides, my book doesn't even mention the law of sines, so this probably isn't the correct method.

Any help would be greatly appreciated.

 

[||spoon||]

It sounds as if (although you didnt mention it) that the box in in static equilibrium??

If this is true then the net force must be zero, decomposing the vectors into two directions (vertical & horizontal) should make this easier

-spoon

 

[Eternal Sky]

That makes things a great deal easier. Thanks for your help!