# Homework Help: I need help with vector addition and subtraction

1. Jul 10, 2010

### ninetyfour

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

Alright so I have an object being pulled from two sides at an angle like the picture below. I want to figure out a third force that can be added to keep the object in the middle of the two sides.

Are the directions of the components I drew correct?

(There is an actual problem for this, I thought I'd put a more general question though)

2. Relevant equations

Vector addition and subtraction

3. The attempt at a solution

I found the horizontal and vertical components of both forces. I then subtracted the horizontal forces from each other because they were going in opposite directions, and added the horizontal vectors because they were going in the same direction. To find the third force, I used the equal but opposite vertical and horizontal forces and found the third net force....

I hope I explained this right :S
Please help me out by telling me if I'm doing this right?

2. Jul 10, 2010

### mynameinc

It depends which force is greater, and by how much.

I like to see that you posted a more general problem, though! It helps you a lot more this way.

If I'm not mistaken (not done this in a long time!), F_3 should be in the direction of the weaker force, and should be equal to F_stronger - F_weaker.

3. Jul 10, 2010

### ninetyfour

Thank you for your help :D

To add a little bit of detail, the problem that I'm looking at has a greater horizontal force on one side, and the greater vertical force on the other.

If I did
V1 - V2 = -V3 (where V1 is the greater vertical force)
and
H1 + H2 = -H3 (since horizontal forces..seem to be pointing the same way, im adding)
Would F3 = the net force of -V3 and -H3?

Are the directions of my components pointing in the right direction in the diagram if the system is moving right?
Am I completely doing this wrong? :P

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