Answers to Questions Posed in Video Activity: Motion Part 2:

Trial A. Roll a steel sphere or a golf ball along the surface of a flat desk. Completely describe (qualitatively, using words such as constant, increasing, decreasing, positive, and negative, for example) the motion of the sphere using all the important terms (displacement, velocity, and acceleration) discussed in the previous presentation.
The sphere moved with a constant velocity (or very close to a constant velocity) as it moved across the desk during its displacement from the starting position. This means that its speed and direction did not change during the motion. Therefore, there was no acceleration.

Trial B. Repeat trial A, this time pushing a book (instead of the sphere) on the flat table.
The book quickly slowed down during its displacement from the starting position. If we define the positive direction as the direction of the displacement, the velocity was positive but the acceleration was negative. Although, it is difficult to know by simple observation, the acceleration seemed to be constant over the motion as the book seemed to slow down in a uniform fashion.

Trial C. Repeat trial A, again with the sphere, this time with the table at a small angle (place something under two of the legs).
The sphere moved with an increasing speed in a straight line. If we define the direction of its motion as positive, the velocity was positive and the acceleration was also positive. Although, it is difficult to know by simple observation, the acceleration seemed to be constant over the motion as the sphere seemed to speed up in a uniform fashion.