Addition of a System of Coplanar Forces

[tophernuts]

1. If the problem statement, all variables and given/known data

The resultant force acting is directed along the positive x-axis, determine the magnitudes of F2 and the resultant force

And that F3x=4 and that F3y=3 (its a right angle 3-4-5 triangle)

Homework Equations

F1=F1_x +F1_Y
F2=F2_x +F2_Y
F3=F3_x +F3_Y

The Attempt at a Solution

F1y= 4cos(30) = 3.464
F3y=3

And since the resultant force is along the x-axis, the resultant y force (Fr_y) would therefore have to equal 0.

But when you run the numbers:

Fr_y=F1_Y+F2_Y+F3_Y
Fr_y=(+3.464)N + (-3)N + F2_y
F2_y= -0.464
xsin30=-0.464
x=-0.464/sin30
x=-0.928

But that is impossible because F2 is above the x-axis and therefore couldn't have a negative y value.

This is where I am currently stuck, if it would work out i could figure out the resultant of F2_y and F2_x which would be F2, and the find out the resultant of all three from there on.Thank you in advance,
Chris

 

[cepheid]

Welcome to PF,

1. If the problem statement, all variables and given/known data
And that F3x=4 and that F3y=3 (its a right angle 3-4-5 triangle)

How do you know that F3 is 30 degrees from the x-axis? Your diagram doesn't indicate such.

 

[tophernuts]

I don't, I just know that it is a 3-4-5 triangle.

I know that F2 is 30 degrees away from the x-axis though

 

[tophernuts]

Well, this is embarrassing.
My friend who I was working on it with and I both failed to see the direction of the arrow F1...
As it is pointing downwards, not upwards, this question makes a lot more sense now...

Sorry for your time!