If the velocity of the object changes from

If the velocity of the object changes from 3 cm / sec to 13 cm / sec in 11 seconds, then at what average rate is the velocity changing?

A cart rolling from rest down a constant incline of length 42 cm requires 8 seconds to travel length of the incline.

What is its average velocity?

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

What therefore is the final velocity of this cart?

What average rate is the velocity of the cart therefore changing?

At what average rate does the velocity of an automobile change, if it accelerates uniformly down a track, starting from rest, and if it requires 16 seconds to cover a distance of 197 meters.