3 forces acting on an object

1. Feb 20, 2015

goonking

http://imgur.com/BFRxPPb

Ok, so I broke up the Y and X components.

F1x =| F2x + F3x| since they cancel each other out.

F3Y = |F2Y + F1Y| since they cancel each other out.

I have no idea what to do from here. Do I need to find the angel of F3 to get somewhere?

2. Feb 20, 2015

Staff: Mentor

There is a template for you to lay out your homework help requests. Please use it.

You seem to have written out all the information needed. Now substitute for the known values.

3. Feb 20, 2015

goonking

what was the point of having the degrees then? are they have any use?

4. Feb 20, 2015

Staff: Mentor

That forms part of the data you substitute in your force relationship expressions.

5. Feb 20, 2015

goonking

so does it look something like this?

F3x = - (( F1 cos 11) + (F2 cos23) )
and
F3y = - ( (F1 sin 11) + (F2 sin23) )

6. Feb 20, 2015

Staff: Mentor

There is some more data that you can substitute, too.

7. Feb 20, 2015

goonking

I wish I knew more data but I don't. This is just very complicated for me lol

8. Feb 20, 2015

Merlin3189

You do know more! You have used the directions of the forces. What do you know about the magnitude of the forces?

9. Feb 20, 2015

goonking

that F1 and F2 are equal? thats about it lol

10. Feb 20, 2015

Merlin3189

So that will simplify the expressions you had.
Since you are asked about F3 : F1 you don't want F2 in your expressions.

11. Feb 20, 2015

goonking

F1x cos 11 + F1y sin 11 = F2y Sin 23 + F2x Cos23

is that have any value?

12. Feb 20, 2015

Merlin3189

F1 and F3 are the ones you want to keep.

13. Feb 20, 2015

Merlin3189

You have so far,
F3x = - (( F1 cos 11) + (F2 cos23) )
F3y = - ( (F1 sin 11) + (F2 sin23) )

You don't want F2, so replace it (you said "that F1 and F2 are equal? thats about it lol" )

Then you also want F3 , but so far you only have F3x and F3y
Now you got from F1x to F1 by noticing that F1x = F1 cos11
You haven't done that for F3x because you don't know the angle, I expect.
But if you look at the diagram and think about it, you DO know the angle. Draw in the resultant of F1 and F2 and work out its angle.
Clue: Since |F1| = |F2| their resultant must be at where? (Symmetry.)