Final answer:
The overall average velocity of an object is calculated by dividing the net displacement by the total time interval. If the net displacement is zero, the average velocity is 0 m/s, but if there is a net displacement, the average velocity uses that displacement to calculate the value.
Step-by-step explanation:
To find the overall average velocity of an object when given its position-time graph, you need to look at the net displacement (change in position) of the object over the total time interval. The average velocity can be calculated as the total net displacement divided by the total time taken for the displacement. If the graph shows that the object has not changed its position over the total time (i.e., the net displacement is 0), then the average velocity is 0 m/s. However, if we have a scenario where the net displacement is given, the average velocity would be that net displacement over the total time.
According to the reference information provided, the total average velocity is 20 m/s, this suggests that over the time interval, the net displacement divided by the time has resulted in an average velocity of 20 m/s.