Average acceleration of a car changing speed and direction

[danielsmith123123]

Homework Statement

A car, travelling initially at 28 m/s [W25 ̊N], takes 8 s to change its velocity to 25 m/s [S]. What is the average acceleration over this time interval?

Relevant Equations

a = vf-vi / t

Nevermind I found what I had to do, thank you though.

 

[Delta2]

You basically have to do one vector subtraction (subtract the 2 given vectors of velocity and keep the result as vector) and then 1 division by 8sec.