A winding stretch of a highway has average speed cameras installed to monitor traffic safety.
The speed limit on this section of the road is 30 m/s30\text{ m/s}30 m/s. The distance along the curved road between two consecutive speed cameras is 2.7 km2.7\text{ km}2.7 km.
Calculate the minimum time, in seconds, it takes a car to travel between the two cameras without exceeding the speed limit.
Explain why the average speed of a car and the magnitude of its average velocity between these two cameras are different.