teacher says the vectors should be added, but I think they should be subtracted

Question

 

A jet plane set to be on a velocity and course of 840 knots, 44 degrees south of west encounters wind. The flight tower shows that their actual velocity and path is 840 knots, 49 degrees south of west. What was the velocity and direction of the wind? I would appreciate multiple answers on this one because I think the teacher worked this problem totally wrong. thanks (:

Answer 1

To solve this problem, it is easier to express each vector in terms of unit vectors i and j.

Let p = velocity of plane = -840 cos 44 i - 840 sin 44 j =

       r = resultant velocity = -840 cos 49 i - 840 sin 49 j =

       w = velocity of wind

Then r = v + w  (vector addition)

or w = v - r =  X + Y

 

Magnitude of w  = sqrt (X ^2 + Y ^2) =

Direction = arctan(Y/X) =

 

Your teacher probably meant r = v + w (correct), or

if you meant w = r - v (correct)

 

 You need a book that have problems of this nature and strategies that can be used to solve them. I recommend "Score High in Physics" which is available on the Amazon website. It is a low cost ebook that can be readily downloaded to ipad, kindle, computer, etc.