NotTim 3 years ago Determine resultant: 25N at 10degrees to the horizontal and 30N horizontally.

1. NotTim

relatively simple. again, i ask for the angle only.

2. NotTim

|dw:1333533030424:dw|

3. experimentX

|dw:1333522316234:dw|

4. experimentX

try using cosine law

5. NotTim

but there are no angles hen (10 isnt' actual an angle within the triangle)

6. experimentX

it's 170

7. NotTim

wut. how?

8. experimentX

because 25 is applied 10 degree to horizontal ... and obviously, it makes 10 degree or 180-10 degree with the horizontal

9. NotTim

ok...but how do i apply 170 in this triangle|dw:1333533509958:dw|

10. NotTim

(im more familiar with that format)

11. experimentX

|dw:1333522738607:dw|

12. NotTim

Like

13. NotTim

|dw:1333533595849:dw|Like I understand how it applies outside, but how do i calculate the angle within?

14. experimentX

30N is parallel to horizontal

15. experimentX

|dw:1333522901720:dw|

16. NotTim

oh. the z,c, f pattern. got it.

17. NotTim

what's our next step then, cos law?

18. experimentX

yep ... we have all parameters required to calculate

19. dumbcow

|dw:1333525849053:dw| another way of looking at it

20. dumbcow

$x^{2} = 25^{2}+30^{2}-2(25)(30)\cos 170$

21. NotTim

thank you! i hadnt thought of this

22. NotTim

hey guys. I'm having problems figuring out the angle (again!)

23. NotTim

I manged to get 5.4 degrees (the closest yet!), while the actual answer is 4.5 degrees.

24. NotTim

i did so by using sin-1(30sin170/54.8)

25. Carniel

Yea he is correct

26. NotTim

what?

27. NotTim

@Carniel Wat?

28. Carniel

What they all said to you is correct

29. NotTim

yeah, but i still got the wrong angle...

30. Carniel

How so? Have you tried Tan,Cos, and Sin?

31. NotTim

the trig ratios? it only applies to right angle triangles...doesnt it?

32. Carniel

Not if I re-call

33. NotTim

Sorry if I sound incredulous, but I really do think it applies only to right angle triangles.

34. Carniel

Do you have notes? If soo check to make sure.

35. NotTim

i dont have the notes specifically on that (its buried in a box somewhere); ill check the internet.

36. NotTim
37. Carniel

There you go then =D

38. NotTim

but...i can't use it here...(unless i do component method, which im not allowed to)

39. Carniel

Which methods do you recall :)?

40. dumbcow

you need to use Law of Sines $\frac{a}{\sin A}=\frac{b}{\sin B}=\frac{c}{\sin C}$

41. NotTim

yeah. i used that and got 5.4 degrees.

42. NotTim

@dumbcow yeah. i used that and got 5.4 degrees.

43. NotTim

hello?

44. dumbcow

ok the 5.4 degrees is the angle inside the triangle, they want the angle of resultant vector --> 10 - 5.45 = 4.55

45. NotTim

thanks again