Question

A car traveling in a straight line has a velocity of 3.79 m/s at some instant. After 5.4 s, its velocity is 11.9 m/s. What is its average acceleration in this time interval? Answer in units of m/s 2

Answer 1

|Acceleration| = (change in speed) / (time for the change)

Change in speed = (speed at the end) minus (speed at the beginning).

Change in speed = (11.9 m/s  -  3.79 m/s)  =  8.11 m/s

|Acceleration| = (8.11 m/s) / (5.4 sec) = 1.502 m/s² (rounded)

This solution is written in terms of speed and the absolute value
of acceleration.  The question gives no information regarding the
direction of motion at any time, so it's not possible to say anything
about velocity, or the direction of acceleration.