## BloomLocke367 one year ago Help with finding Resultant vectors using trig? I kind of know what I'm doing but I want verification I'm doing it correctly.

1. Jaynator495

*whistles while waiting*

2. Jaynator495

annnyyyy day now...

3. Jaynator495

and im waiting and im waiting and im waitng...

4. Jaynator495

TYPE FASTER!!!! xD

5. BloomLocke367

$$F_1=6.7~N~@ ~54°~W~of~N$$ $$F_2=9.2~N~@ ~26°~W~of~S$$

6. Jaynator495

Jeese i go to help in math for the first time in a long time and people take forever to post the question! xD

7. BloomLocke367

sorry XD I had to look up the code for the degree sign

8. Jaynator495

XD

9. BloomLocke367

I'm pretty sure I have to add $$90°$$ to the first one because it's in the 3rd quadrant and you always start in the first for these problems (this is technically physics but it's still math lol)

10. Jaynator495

you help them peachpi lel

11. Jaynator495

*laughs away*

12. BloomLocke367

I know I have to separate it in components and I do that using trig.. so.. hang on.. this will take some time for me to type out lol. please be patient.

13. IrishBoy123

draw it :p quicker/easier

14. BloomLocke367

I can't.. my cursor goes BEHIND google chrome.. so I have to type it. /sigh

15. Jaynator495

um, out of curiosity, is it a piticulair site orrr...

16. BloomLocke367

17. BloomLocke367

sorry

18. Jaynator495

LMAO

19. BloomLocke367

anyhoo.. let me do math cx

20. Jaynator495

i still dont know what to tell you... *laughs !!half!! to !^death^!*

21. BloomLocke367

$$F_{1x}=6.7Cos(144)\\F_{1y}=6.7Sin(144)\\ F_{2x}=2.9Cos(244)\\F_{2y}=2.9Sin(244)$$ I know I then have to add $$F_{1x}$$ and $$F_{2x}$$ and add $$F_{1y}$$ and $$F_{2y}$$.

22. BloomLocke367

@IrishBoy123

23. BloomLocke367

is that correct so far?

24. BloomLocke367

@phi

25. phi

yes, that looks good

26. BloomLocke367

okay so when I added $$F_{1x}$$ and $$F_{2x}$$ I got -1.48... but I have a calculator on my phone and I don't know if it's in radians or degrees so I'm not sure that's right...

27. phi

up top you said F2 is 9.2 and in your calculations you are using 2.9 which is it ?

28. BloomLocke367

dang it.. it's 9.2.. I accidentally wrote 2.9 :/ okay let me redo them.

29. BloomLocke367

-9.45?

30. phi

yes, for the x value

31. BloomLocke367

okay now for y...

32. BloomLocke367

-4.33?

33. phi

yes

34. BloomLocke367

so then I take $$F=\sqrt{(-9.45)^2+(-4.33)^2}$$ right?

35. phi

if you want the magnitude, yes

36. BloomLocke367

yes that is what we are looking for at this moment. I'll find the degree next using tangent.

37. BloomLocke367

I got 10.39. is that right?

38. BloomLocke367

and I got 8.01° for the angle measure.. but both x and y are negative.. so it needs to be in the 3rd quadrant and is currently in the first.. so I have to add 180, correct? to get 188.01°

39. BloomLocke367

wait.. that doesn't matter because they gave direction.. so instead I would just say 8.01° N of E, right?

40. BloomLocke367

I don't know. .this is where I get confused.

41. phi

you probably want to use 3 decimals in the calculation if you want 2 digit accuracy I get mag 10.4 (rounded 10.3979) No I did not get 8 degrees type into google atan(4.331/9.453) in degrees =

42. BloomLocke367

wait.. why did you use those numbers? I used -4.33 and -9.45..

43. phi

|dw:1443212499462:dw|

44. BloomLocke367

wait nevermind *facepalm*

45. phi

I used 3 digits (you can always round down later) I ignored the 2 minus signs because they cancel each other

46. BloomLocke367

I SEE WHAT I DID. I typed 1.33 and not 4.33 XD

47. BloomLocke367

24.62?

48. phi

yes, and that will be 24.6 degrees south of west or 65.4 degrees west of south

49. BloomLocke367

wait.. why is it south of west?..

50. phi

|dw:1443212895471:dw|

51. BloomLocke367

I thought what we calculated was 24.6° N of E... and we would have to figure out S of W.. but I don't know.

52. BloomLocke367

Is it because I added what I needed to in the beginning? so I don't have to at the end?

53. phi

you changed 54º W of N to 144º (measured as we do in math, counter clockwise from the positive x-axis). similarly you changed 26º W of S to 244º now add the vectors (head to tail) |dw:1443213168068:dw|

54. phi

you found the components of the dark vector <9, -4> it is pointing south of west. if we find the angle it makes with the (negative) x-axis we get 24.6º

55. BloomLocke367

ohhh okay. I think I understand a little bit better. My main issue is figuring out what direction/angle the resultant vector is going.

56. phi

using formulas (as you did) and drawing the vectors are very different ways of solving the problem. If you do it both ways, it is a good way to check your results. the picture gives you a rough idea of the answer and the formulas give the exact numbers.

57. BloomLocke367

Alright. The next one has 3 vectors.. I generally understand these they just take me a very long time to do them. :/

58. BloomLocke367

Do you mind if I open a new question and tag you?

59. phi

yes, a new post is better