1. The problem statement, all variables and given/known data A car with a velocity of 25 m/s [E] changes its velocity to 25 m/s in 15s. Calculate the car's average acceleration. 2. Relevant equations a = v/t 3. The attempt at a solution The problem I'm having with this question (And actually, vectors in general) is the direction in the end. I understand how to obtain both the magnitude and angle, but the answer says 2.4 m/s2 [45º S of W]. Here's what I have: I drew out the vectors for when the car moves 25 m/s [E] and when it moves 25 m/s , putting the second vector to the tip of the one facing east. If I draw the resultant vector by having it go from the tail of the vi and to the tip of vf, I have the right angle triangle that I can solve. But my problem is, the resultant vector is pointing to the east of south, which is clearly wrong. Does the direction change when I find acceleration? Thank you!