If the velocity of the object changes from 5 cm / sec to 14 cm / sec in 9 seconds, then at what average rate is the velocity changing?

It  requires 5.1 seconds, starting from rest, for a ball to roll the 38 centimeter length of a uniform incline.

An object which accelerates uniformly from rest will attain a final velocity which is double its average velocity.

At what average rate does the velocity of an airplane change, if it accelerates uniformly down a runway, starting from rest, requiring 10 seconds to cover a distance of 154 meters.