Reflection from such a rough surface is called diffuse reflection and appears matte
Use the distance swan and the time elapsed in that interval.
Average velocity = distance / time
Average velocity = [4.0 m + 3.0m] / 3.2 s = 2.1875 m/s
When someone lifts a book from the ground, the work you use is positive. By lifting the book, you change it's energy and it's original place The book gains, kinectic energy.
Hope I helped.
