## ashna 2 years ago A motor boat is rising towards N at 25 Km/hr and the water current in that region is 10 km /hr in the direction of 60° east of south . Find the resultant velocity of the boat .

1. ashna

@waterineyes you know this sum ?

2. waterineyes

I don't...

3. ashna

you know some one in open study who can help me ?

4. waterineyes

5. ashna

i sent him a msg .. no reply :/

6. waterineyes

But he is online.. Let me try..

7. ashna

okay !

8. waterineyes

Which chapter is this ??

9. ashna

motion in a plane.

10. waterineyes

Yeah I think you will get help here..

11. ashna

thanks waterineyes :)

12. waterineyes

@rsadhvika do you know how to solve this ??

13. waterineyes

|dw:1344771481322:dw|

14. waterineyes

Here A and B are the vectors.. A is representing the boat and B is representing Water...

15. ashna

okay .. understood !

16. waterineyes

Now We have to find Resultant first.. For that we first make our figure look like parallelogram..

17. ashna

okay

18. waterineyes

Wait I draw the figure more clearly for you..

19. ashna

its okay .. i can understand :)

20. waterineyes

|dw:1344771854805:dw|

21. ashna

|dw:1344771963782:dw|

22. ashna

is that the parellelogram we need ?

23. waterineyes

Now make it look like parallelogram: |dw:1344771989674:dw| Getting this ??

24. ashna

yeah got it !

25. waterineyes

Now can you draw diagonal of the parallelogram ??

26. ashna

|dw:1344772085729:dw|

27. ashna

wrong ?

28. waterineyes

Great.. This is the resultant of A and B vector..

29. ashna

okay :)

30. ashna

what is theta here ?

31. waterineyes

You must mention the direction also..

32. ashna

what direction ? direction of vector ?

33. waterineyes

|dw:1344772213529:dw|

34. ashna

okay !

35. waterineyes

Since boat has higher velocity then boat will go in upward direction.. Getting ??

36. ashna

yeah ..and if lower velocity , down ?

37. waterineyes

Yeah that will depend upon velocity of water..

38. ashna

okay !

39. waterineyes

Have you studied about the formula: $Resultant (R)= \sqrt{A^2 + B^2 + 2AB \cos(\theta)}$

40. ashna

yeah i have !

41. waterineyes

Here A is just velocity of boat that is : 25 and B is just velocity of water that is : 10 But you have to find theta first.. Right ??

42. ashna

yeah .. how do we find theta ?

43. waterineyes

Theta is basically angle between the two vectors A and B.. Here what is the angle between A and B.. Can you locate on the drawing ??

44. ashna

|dw:1344772636899:dw|

45. ashna

i don't know !

46. ashna

|dw:1344772698399:dw|

47. waterineyes

That is the angle between A and the resultant.. We have to locate angle between A and B..

48. waterineyes

Don't worry @ashna I draw it..

49. ashna

okay !

50. waterineyes

|dw:1344772809427:dw| Getting?? That is the angle between A and B..

51. ashna

yeah !

52. waterineyes

Can you find its value ??

53. waterineyes

Make a try..

54. ashna

180 - 60 ?

55. ashna

120 ?

56. waterineyes

Great.. A medal for you..

57. ashna

:)

58. waterineyes

Can you tell cos(120) = ??

59. ashna

yea .. cos (90+30) - sin 30 - 1/2 correct ?

60. waterineyes

I wish I could give you more medals.. Yes that is very correct.. Now can you use that formula ??

61. ashna

okay i'll try !

62. waterineyes

There is no need to go fast.. I can wait.. Just take your time and post your answer here..

63. waterineyes

I think this site is going to be down soon..

64. waterineyes

If my reply does not come @ashna then don't worry . Just post the answer or doubt here I will check it later on..

65. waterineyes

What happened @ashna

66. ashna

okay .. now i can type .. some net problem i guess.. sorry for the delay .. i got square root 475 !

67. ashna

91.7945