• Support PF! Buy your school textbooks, materials and every day products Here!

Vector addition and subtraction. feeling stupid for being confused over this

  • #1

Homework Statement



A = 2i + 3j
B = -5i + 6j

Calculate (draw vector diagram)
A + B
A - B

Homework Equations



actually we're just confused as to whether we need to use the angles to answer this or just answer it directly, meaning that for A + B the answer would be -3i + 9j

The Attempt at a Solution



do we use

A + B = -3i + 9j

or solve for the angles(*rounded off) and use

A+B = ((√13)cos56 + (√61)cos50)i + ((√13)sin56 + (√61)sin50)j

????????
 

Answers and Replies

  • #2
Simon Bridge
Science Advisor
Homework Helper
17,847
1,644
Try drawing the vectors on graph paper, and adding/subtracting head-to-tail.
They are simple enough to do this, and it will clear up your confusion.

The vectors are provided to you in Cartesian representation. If you do it by angles, you want the polar representation. These are entirely equivalent and will get you the same answers. (provided you worked out the angles correctly - yours are all in the 1st quadrant but the vectors are not... one is in the 4th quadrant so it's angle is greater than 270 degrees - I have not checked that you've accounted for this.)
 
Last edited:
  • #3
SteamKing
Staff Emeritus
Science Advisor
Homework Helper
12,798
1,666
The problem statement asks you to 'draw vector diagram' for A+B and A-B. Did you do that?
 

Related Threads on Vector addition and subtraction. feeling stupid for being confused over this

  • Last Post
Replies
2
Views
4K
  • Last Post
Replies
7
Views
2K
Replies
4
Views
822
Replies
3
Views
397
Replies
7
Views
775
Replies
1
Views
1K
Replies
2
Views
3K
Replies
1
Views
4K
  • Last Post
Replies
7
Views
512
Top