Abird flies north with a force of 11n, the air resistance is 2n. show the vectordiagram, with the magnitude and displacement indicated clearly.

In this item, we take the direction of the bird, given to be north, to be the positive side. In the opposite is the direction of the air (south), we take as negative. The vectors are now,
   + 11 (bird) and -2 (air)

The sum of he vectors is equal to the sum of the two numbers. That is equal to +9. Thus, the magnitude is equal to 9 and the direction is +.