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Adding Vectors

  • #1
I JUST started adding vectors.. as in.. last class. I got a ton of questions, and have done three of them. The answers are given, but I got them wrong. I'll follow the little template already given:

Homework Statement


What is the net force on a stack of books which are applied two forces: 2.0 N 61 degrees N of W and 59 degrees N of E?

The answer is 75.0 N, 73 degrees (N of E)

Homework Equations


??


The Attempt at a Solution



http://img245.imageshack.us/img245/5965/vectorsao5.jpg [Broken]

Thanks in advance!
 
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Answers and Replies

  • #2
203
0
Have you heard of the parallelogram rule yet?
 
  • #3
Have you heard of the parallelogram rule yet?
Who in the what? :S

I've never heard of that...

My teacher just did one example on the board, we copied it down as fast as we could, and now I'm trying to do what I think she did...which is what I attempted.

LOL I'm assuming I'm missing something obvious that I've never heard of before.

Thanks

edit: BTW, I'm in Grade 11 and have barley learned anything above the basics.
 
  • #4
203
0
Maybe that is for the resultant.

Anyways, you can just put them head to tail(like I think you did)....and then solve them similar to how your find the hypotenuse on a right triangle.
 
  • #5
Maybe that is for the resultant.

Anyways, you can just put them head to tail(like I think you did)....and then solve them similar to how your find the hypotenuse on a right triangle.
Thanks for the response, but I'm not quite sure what you mean... can you see what I did wrong?
 
  • #6
cristo
Staff Emeritus
Science Advisor
8,107
73
Well, firstly, you're using x's and y's to mean different things on each diagram! Pick a coordinate system (the most conventional is that x components are horizontal, and y components are vertical) and stick to it!

Now, the horizontal components are in opposite directions, so the resultant will be V2x-V1x.

You seem to be close, so try again, this time sticking to a convention, and see how you do.
 
  • #7
Well, firstly, you're using x's and y's to mean different things on each diagram! Pick a coordinate system (the most conventional is that x components are horizontal, and y components are vertical) and stick to it!
:O

Holy moly.... I haven't made that idiotic mistake since grade 8! And the first time I post a question like this on a forum, It's my lucky day and I do it for the first time in 3 years!

Yes, thanks for pointing that out. I was able to get it.

There's another 2 questions that have nothing to do with mixing up the x/y axis (lol), so they are still problems (I was hoping there was a solution to why all 3 were incorrect)

Thanks

Before posting any more problems, I'll go back and retry the other two to check for more embarrassing mistakes...

This is comparable to last semester when I was frustrated with a single problem involving intersections of circles and lines in Math... only to have somebody point out that I had "1 x 1 = 2". LOL
 
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