1. ## Vector problem

A force of 36N pulls at an angle of 20 degrees above due east. Pulling in the opposite direction is a force of 48N acting at an angle of 42 degrees below due west. Find the magnitude and direction of the resultant force.

To start off, should I add or subtract the vectors?

2. ## Re: Vector problem

Yes.

One may wish to break the forces into their orthogonal projections. (North-South and East-West) It should be relatively obvious from there.

3. ## Re: Vector problem

Here is a crude diagram that I made of the problem:

Is this correct?

4. ## Re: Vector problem

And I meant -42 degrees.

5. ## Re: Vector problem

No good. Go 42º south of west, not 42º west of north.

6. ## Re: Vector problem

42 degrees south of west is -42 degrees, no?

7. ## Re: Vector problem

No, that's 42º West of North. Start at Due West, which is already -90º. You need -132º = -90º-42º.

8. ## Re: Vector problem

Now I'm confused. I thought 42 degrees west (left) of north would be 132 degrees because it would be 90 + 42.
And if I started at the negative x-axis (or "due west"), wouldn't I be making a 180 degree angle? If I were making a 270 degree angle, I would be starting at the negative y-axis.

9. ## Re: Vector problem

Ahh nevermind, sorry. I should have looked up what due west and due east meant.....

10. ## Re: Vector problem

These definitions are normally included in what we like to call "General Knowledge". :-)

11. ## Re: Vector problem

Pff. If you say so. I just don't get why North is 0 degrees, when on a grid that would be East.

12. ## Re: Vector problem

Yup. Something you do have to get used to. It's just a convention. There are other interesting conventions you will encounter from time to time.