## anonymous 4 years ago What is the magnitude of the force on the -10 charge in the figure ?

1. anonymous

|dw:1327758982728:dw|

2. anonymous

the resultant force should be...|dw:1327759214456:dw| something like that

3. anonymous

broke down x and y components for force on + on - and - on - and then added...not getting right answer

4. anonymous

450*10^-9 N

5. anonymous

can you explain?

6. anonymous

7. anonymous

why?

8. anonymous

it is not easy. it is a vector quantity. therefore you must have to consider directions.

9. anonymous

you have to wait until i solve it for you. ok elicia85?

10. anonymous

sure and can you please show steps??

11. anonymous

yes i will show steps to you. wait. i am here.

12. anonymous

ok thank you

13. anonymous

you are welcome.

14. anonymous

here is diagram first look at this and understand this.

15. anonymous

is this pic making sense to you? if i do anything wrong here then kindly point out me. you too faryad, hei, elicia85 and an unknown person.

16. anonymous

looks good

17. anonymous

thank you Shayan

18. anonymous

wait i have to go and just come in 2min

19. anonymous

hello. it is taking too much time for me. lets solve step by step here. ok. force of +15nC will be represented by F15 force of -10nC will be represented by F10 force of -5nC will be represented by F5 ok.

20. anonymous

now as you can see. on -10nC there are two forces acting on it. 1)F15 which is attractive and at an angle of 45 2)F5 which repulsive.

21. anonymous

F15 can be resolve into factors. along x-axis and along y-axis.

22. anonymous

forces along y-axis can be calculated as, F15y=(kq1q2)/r² sin45 and F5y=(kq1q2)/r² forces along x-axis can be calculated as, F15x=(kq1q2)/r² cos45

23. anonymous

24. anonymous

have you got it? it is done.

25. anonymous

it's exactly what i did but i will try again

26. anonymous

27. anonymous

well you still have to add the F5 on F10 don't you? which will only consist of y direction force

28. anonymous

29. anonymous

well you still have to add the F5 on F10 don't you? which will only consist of y direction force on y-axis: F10y=F15sin45 - F5 on x-axis: F10x= -F15x finally, $F _{10}=\sqrt{(F _{10y})^{2}+(F _{10x})^{2}}$ This is complete.

30. anonymous

any question?

31. anonymous

shayan can you help me?

32. anonymous

of course fryad. although we are brothers. arn't we?

33. anonymous

thank you i'll try again!

34. anonymous

you are ever welcome. Regards, Read my Profile. :D

35. anonymous

yes ,sure thank you , please prove this for me A.B=cos& |A|.|B|

36. anonymous

ok w8. let me analyze.

37. anonymous

The three vectors above form the triangle AOB. using Law of Cosines , $|a-b|^{2}=|a|^{2}+|b|^{2}-2|a||b|\cos \theta$ using properties of dot product. $|a-b|^{2}=(a-b).(a-b)$ $=a.a-a.b-b.a+b.b$ $=|a|^{2}+|b|^{2}-2a.b$ original becomes, $|a-b|^{2}=|a|^{2}+|b ^{2}|-2|a||b|\cos \theta$ and, $|a|^{2}-2a.b+|b|^{2}=|a|^{2}+|b ^{2}|-2|a||b|\cos \theta$ now cancel terms which are same and you will got $a.b=|a||b|\cos \theta$

38. anonymous

that is all. Regards, Read my Profile. :D

39. anonymous

zor zor supas aziyatm dait

40. anonymous

kia?

41. anonymous

what is this language?

42. anonymous

43. anonymous

urdu and english.

44. anonymous

I am kurdish

45. anonymous

ok. now good luck. take care everyone.

46. anonymous

I am beginner in physic,thus I want help me for any time if you can my brother?

47. anonymous

sure sure. i am often available here. you can post your question.

48. anonymous

That is all kind of you for every thing.can I recognize you in facebook?

49. anonymous

Just skimming through this.... You should recognize that the angle is not 45 degrees because it's a rectangle, not a square, so the values above would not yield the correct answer.

50. anonymous

good point, i wasn't using 45 though, just used the measurements given. i still need to resolve, haven't got to it yet

51. anonymous

elica85 are you here?

52. anonymous

oh yes. so angle is not 45degree. it can be calculated as, $\tan^{-1} (0.01/0.03)=18.43degrees.$ Kindly use this angle instead of 45.

53. anonymous

thanks to Jemurray3.

54. anonymous

elica I assume you are adding the components separately and then using the Pythagorean Theorem to calculate the magnitude of the resultant, right?

55. anonymous

hi jemurray3

56. anonymous

Hi there Shayaan

57. anonymous

http://openstudy.com/study#/updates/4f245a39e4b0a2a9c2667f2f We need you in mathematics section. kindly help us.

58. anonymous

thank you everyone, i did get the right answer finally. i was confused about +/-. i thought the - charge on negative would make it negative direction going down y, making it double negative...so i was just getting calculations wrong. it was 18 degrees ^^

59. anonymous

you are ever welcome. we are made for help. pleasure.