An object travels North at #3 m/s# for #8 s# and then travels South at #4 m/s# for # 2 s#. What are the object's average speed and velocity?
We must recall the definitions of average speed and average velocity.
Average speed: the change in distance divided by the total time
Average velocity: the DISPLACEMENT divided by the total time
remember that DISPLACEMENT is the distance from the initial point and the final point. So if I ran one lap around the track field, my displacement would actually be .... 0 meters.
So, we want to find the total distance that we traveled, both North and South.
traveling 3 m/s for 8 s would mean that we traveled for 24 meters total, North.
traveling 4 m/s for 2 s would mean that we traveled for 8 meters total, South.
Therefore, our total distance is 32 meters. The time it took was 10 seconds (8s north and 2s south), so the average speed is
Our total DISPLACEMENT is going to be 24 north + 8 south, or basically if we take north as the positive direction,
Our total time is still 10 seconds, so our average velocity is