Mechanics question (vector descriptions of two birds' flight paths)

[trew]

Homework Statement:

as below

Relevant Equations:

as below

Part (a) was fine.

For part (b), I started off with finding the position vector of bird A and bird B after 4 seconds, and this was:

Position vector of A after 4 seconds: -4i + 11j

Position vector of B after 4 seconds: (-8 + 4p)i + (9+8p)j

But after this I'm lost.

Usually I'd have some idea but honestly right now I have no idea. What am I missing here?

 

[kuruman]

The statement "bird B is south west of bird A" can be interpreted to mean that the position vector of bird B relative to bird A is at 45^o West of South. If you can find an expression for that vector at t = 4 s, you should be able to find p and hence the speed of bird B.