# Homework Help: Finding the force needed for equilibrium.

1. Sep 14, 2011

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

5. Find the magnitudes of the forces F2 and F3 that you would need to balance a 2.45 N force at 0.0 degrees If the angle of F2 is 35.0 degrees and F3 is 50 degrees.

2. Relevant equations

F2 cos 35 degrees - F3 cos 50 degrees =0

F2 sin 35 degrees -F2 sin 45 degrees -mg= 0

3. The attempt at a solution

-.25 =m
g= 9.80 m/s2

F2 cos 35 degrees - F3 cos 50 degrees =0
F2 sin 35 degrees -F2 sin 45 degrees = 2.5

Is this set up right? Thanks.
Is there a better way to calculate the forces to find equilibrium?

Last edited: Sep 14, 2011
2. Sep 14, 2011

### PeterO

I would need to know what your angles are measured with respect to??

3. Sep 14, 2011

angle between f2 and f3 are 85 degrees. f2 is 35 degrees, and f3 is 50 degrees. 3 forces are acting on each other. f1 is just a straight line between them.

Last edited: Sep 14, 2011
4. Sep 14, 2011

### PeterO

OK the angle between f2 and f3 you have stated.

f2 is 35 degrees. 35 degrees to what?
f3 is 50 degrees. 50 degrees to what?

Try giving True bearings. 0 degrees is North, 90 degrees is East, 180 degrees is South, 270 degrees is West.

5. Sep 14, 2011

35 degrees north of west
50 degrees south of west

6. Sep 14, 2011

### PeterO

OK then

I am assuming then that f1 it due East.

The vertical components of f2 and f3 must be equal in magnitude - they are already opposite in direction
The horizontal components of f2 and f3 must add to 2.45 N to balance f1.

7. Sep 14, 2011

Would mg/sq. root 2 work?

8. Sep 14, 2011

### PeterO

I don't thing so. You need sine and cosine functions to work out the components

9. Sep 14, 2011

ok thanks!

10. Sep 14, 2011

I received 3.87 N for both f2 and f3 magnitude.

Last edited: Sep 14, 2011
11. Sep 15, 2011

### PeterO

I can't see that they would be equal.

Can you confirm that 2.45 N East is the only other force involved.

It this whole thing on a horizontal plane or is there a weight hanging somewhere/some how?