1. Feb 8, 2008

### suki86

1. The problem statement, all variables and given/known data
i have 3 force vectors i want to add to get the resultant.
vector a mag=1.31N and is 51.34deg to the x-axis (Quad 1)
vector b mag= 1.31N and is 51.34deg to the x-axis (Quad 4)
vector c mag = .719N and is along the pos y axis

how do you add these for resultant???
ive learned this before but forgot how to add them, --isnt there a simple way to get the one resultant vector?
thanks for any help!

2. Relevant equations

3. The attempt at a solution

2. Feb 8, 2008

### suki86

also, the forces are from point charges, so no gravity

3. Feb 8, 2008

### Dick

Split them all into x and y components and then add the components to get the components of the sum.

4. Feb 8, 2008

### suki86

ok but isnt there a faster way to get the resultant rather than breaking them apart then putting back together again?

5. Feb 8, 2008

### suki86

Fxa = 1.31N * cos 51.34deg = .818353N
Fxb = 1.31N * cos 51.34deg = .818353N
Fxc............................ = 0 (because force is along the y-axis)

Fya = 1.31N * sin 51.34deg = 1.0229N
Fyb = 1.31 * sin51.34deg = 1.0229N
Fyc = .719N = .719N (because along the y-axis)

6. Feb 8, 2008

### suki86

ok so, I broke them down into x and y components. just need help adding them now?
thanks!

7. Feb 8, 2008

### =CIA= h1tman

I'm pretty sure you have to use basic trig functions to find the lengths. Then, add them together.

8. Feb 8, 2008

### Dick

Ok, so now add all of the x's and all of the y's. That gives you the x and y components of the total force T. Do you need to get the total magnitude and direction of T? Do you know how to do that?

9. Feb 8, 2008

### suki86

yeah total magnitude is what i want.
So Fx = 1.636706
Fy = 2.7648

ho do i add them? thanks

10. Feb 8, 2008

### Dick

Good so far. You don't 'add' them. The vector is (Fx,Fy). The magnitude is sqrt(Fx^2+Fy^2), the angle is arctan(Fy/Fx). It's the opposite of splitting into components, you are 'recombining' the components.

11. Feb 9, 2008

### suki86

oh duh. this is just pythagarus isnt it? i mean x and y components mean i just get the hypotenuse and thats how you "add" them right>?
so, sq rt Fx^2 + Fy^2 = resultant vector

12. Feb 9, 2008

### suki86

i mean the MAGNITUDE of the vector at least.

13. Feb 9, 2008

### Dick

Yes. You are on the right track.