Calculate change in velocity?

Question

A car being driven north at 12 ms rounds a corner so that it is now being driven west and 16 ms. Calculate the change in velocity of the car?

Ok, so im not sure how to set this out. Is it just 4ms (16 -12) or do i use Pythagoras to get 20ms

And if it is 20 ms, would the answer be 20 ms at 53.1 degrees to 12ms?

Im not sure how to answer this question. Any help is appreciated :)

Answer 1

Using a triangle ABC of forces with angle B = 90 deg, A north of B and C west of B, AB = 12 represents the initial velocity, BC represents the final velocity, and AC represents the change.

The change is 20 m/s, as ABC is a 3-4-5 triangle in direction AC, which is west of south by angle BAC = arctan(4 / 3) = 53.1 deg.

It is better to state the actual direction, as 53.1 deg. to the 12 m/s leaves the direction rather ambiguous.