On the position-time graph, what is the average velocity between 5 s and 10 s?
a.+2.0 m/s b. +4.0 m/s c.8.0 m/s d.3.0 m/s

For this case, we observe that in the interval of 5 to 10 seconds the behavior of the function is linear. Therefore, the average speed in that interval will be given by the slope of the line. This can be calculated as follows
 m = (y2-y1) / (x2-x1)
 Substituting the values of points A and C
 m = ((30) - (10)) / ((10) - (5)) = 4
 answer
 the average velocity between 5 s and 10 s is 4m / s
 B. +4.0 m / s