# Forces In Equilibrium

1. Aug 13, 2009

### noobish

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

http://img31.imageshack.us/img31/3926/71072701.jpg [Broken]

I need to find the value of F2. I have drawn the free body diagram, and to find F2,

F2 cos 30 + F3 sin 30 = 10N
F1 cos 30 + F2 sin 30 = F3 cos 30

I used this method, and tried to solve it but it doesn't lead me to the answer. Anyone can guide me? Thanks.

2. Relevant equations

3. The attempt at a solution

Last edited by a moderator: May 4, 2017
2. Aug 13, 2009

### Pupil

Rotate your axis so that the F1 and F3 are exclusively in the x plane. From there it should be easy. You know the force of gravity, and you can find it's i and j components and solve for the rest. That's the trick to these inclined plane problems -- choose your axis wisely.

3. Aug 13, 2009

### kuruman

First draw yourself a coordinate system (x and y axes) so that we can talk about components of vectors. For a problem of this sort, x is usually along the incline and y perpendicular to it.

Once you've done that, find the components of each vector. Since the object is at rest, the sum of all the x components must be zero and the sum of all the y components must be zero.

Note that for a sum of two terms to be zero, one term must be positive and the other negative. Your equations do not show that, With a coordinate system drawn, it should be easy to see which components are positive and which are negative.

4. Aug 13, 2009

### noobish

Thanks a lot guys. I've got it.