To know how fast is the motorcycle traveling between t = 1 and t = 3 seconds, we need to find the slope of the graph, so using the position for t=1 and t=3, we get:
[tex]\text{velocity = }\frac{60\text{ meters}-20\text{ meters}}{3\text{ seconds}-1\text{ second}}=\frac{40\text{ meters}}{2\text{ seconds}}=20\text{ meters/sec}[/tex]
Because at t=1 the position is 20 meters and at t=3 the position is 60 meters.
Answer: 20 meters per second
